Glossary of Automotive Terms – B

Letter B – Dictionary of Automotive Terms

  1. Symbol for susceptance in an AC circuit (unit is the siemens; measured by the negative of the reactive component of the admittance
  2. Symbol for magnetic flux density in a magnetic circuit (unit is the tesla; 1T=1 Wbm-2=1 Vsm-2).
An abbreviation for Battery positive voltage used to designate positive voltage at aor near the battery level.
An abbreviation for British Association which is a term used to describe a series of fine, small diameter threads for electrical and precision equipment.
An Alloy of tin, copper, and antimony having good antifriction properties. Used as a facing for bearings.

Babbitt metal
Babbitt’s metal
A bearing alloy originally patented by Isaac Babbitt, composed of 50 parts tin, five antimony, and one copper. Addition of lead greatly extends range of service. Composition varies widely, with tin 5-90%, copper 1.5-6%, antimony 7-10%, lead 5-48.5%.
Colloquial term for a co-signer or co-buyer on an automobile purchase contract.
Babcock and Wilcox boiler
A water-tube boiler consisting in its simplest form of a horizontal drum from which is suspended a pair of headers carrying between them an inclined bank of straight tubes.
Babo’s law
The vapor pressure of a liquid is lowered when a non-volatile substance is dissolved in it, by an amount proportional to the concentration of the solution.
A small incandescent spotlight used in film and television production.
Baby seat

Baby SeatBaby Seat

A specially designed seating device (which is not generally standard equipment) to hold safely very young children (usually under the weight of 10 kilograms).

  1. Abbreviation for Blood Alcohol Content
  2. Abbreviation for bypass air control system
  3. Abbreviation for Bypass air control valve
A large vat used in various industries, such as dyeing, soap-making, and brewing. Also spelled beck

Back ampere-turns
That part of the armature ampere-turns which produces a direct demagnetizing effect on the main poles. Also called demagnetizing ampere-turns
Back annealing
Controlling the softening of a fully work hardened metal so as to produce the desired degree of temper by partial recrystallization.

Back axle
The rear axle.
Back axle ratio
Back band
The outside member of a door or window casing.
The major long-distance, multi-channel link in a telecommunication network, from which smaller links branch off

Backbone chassis
Backbone frame

Backbone FrameBackbone Frame

  • A vehicle frame, having the cross-section of a rectangular box, that runs along the center of the vehicle and occupies the space between the seats.
    • This box generally divides at the front, running along each side of the gearbox and engine up to a crossmember to which the front suspension pieces are attached.
    • At the rear a similar triangular frame encloses the final-drive housing and provides attaching points for the rear suspension.
    • Lightness combined with high Torsional rigidity are features of this frame design, made famous by Colin Chapman with the Lotus Elan.
  • In a motorcycle, a frame which uses the engine as a structural member.
Backbone network
A high-capacity computer network that links together other networks of lower capacity. Fiber optic cables are often used to form these links.
Back coupling
Any form of coupling which permits the transfer of energy from the output circuit of an amplifier to its input circuit.


Back diode
Back edging
A method of cutting a tile or brick by chipping away the biscuit below the glazed face, the front itself being scribed.
Back EMF
The EMF which arises in an inductance (because of rate of change of current), in an electric motor (because of flux cutting) or in a primary cell (because of polarization), or in a secondary cell (when being charged). Also called counter EMF
Back-emf cells
Cells connected into an electric circuit in such a way that their emf opposes the flow of current in the circuit.
Back emission
Emission of electrons from the anode.
Back end
When the dealer sends a vehicle purchase contract to the bank for financing, the dealer is given an extra bonus (the back end) from the bank for choosing this bank.
Materials used to replace previously excavated material.
  1. Passage of unburned fuel mixture into the exhaust system where it is ignited and causes an explosion (backfire) prematurely.
  2. Sometimes Ignition takes place in the intake manifold by a flame from a cylinder because the intake valve leaks. Burning of the fuel mixture in the intake manifold may be caused by faulty timing, crossed plug wires, leaky intake valve, etc.
  3. A welding term referring to a short pop of the torch flame followed by extinguishing of the flame or continued burning of the gasses.
Repeated backfires in the exhaust or the cylinders.
Making changes to nuclear (and other) plants already designed or built, e.g., to cater to changes in safety criteria.
Back-flap hinge
A hinge in two square leaves, screwed to the face of a door which is too thin to permit the use of a butt hinge.
Backflow scavenging
Pushing fluid in a direction opposite of normal flow. This is done for cleaning the engine’s cooling system.

Back focus
The distance between the rear surface of a lens and the image of an object at infinity.
Back gear
A speed-reducing gear fitted to the headstock of a belt-driven metal-turning lathe. It consists of a simple layshaft, which may be brought into gear with the coned pulley and mandrel when required.
Extraneous signals arising from any cause which might be confused with the required measurements, e.g., in electrical measurements of nuclear phenomena and of radioactivity, it would include counts emanating from amplifier noise, cosmic rays and insulator leakage.
Background job
A task having a low priority within a multiprogramming system.


Background noise
Extraneous noise contaminating sound measurements and which cannot be separated from wanted signals. For example residual output from microphones, pickups, lines giving a signal-to-noise ratio. Also called ground noise
Background radiation
Radiation coming from sources other than that being observed.
Background video
(BGV) A technique for overlaying video on previously recorded depth multiplex audio. Also called video on sound (VOS).
Backhand welding
Welding in the direction opposite to the direction that the gas flame is pointing. Also called backward welding.

Back Haul
  1. After an outbound shipment has been delivered, the truck will return empty. In order to generate more revenue, the dispatcher may find a shipment for the return which is the back haul.
  2. Movement in the direction of lighter traffic flow when traffic generally is heavier in the opposite direction.
  3. To move a shipment back over part of a route already traveled.
Excess heating of a cathode due to bombardment by high-energy electrons returning to the cathode. In magnetrons, it may be sufficient to keep the cathode at operating temperature without external heating.
  1. Some material placed on the root side of a weld to aid control of penetration.
  2. Light-absorbent layer on the rear surface of photographic film or plate to reduce unwanted exposure
  3. A meterological term describing the changing of a wind in a counter-clockwise direction.


Backing boards
Wedge-shaped wooden boards between which an unbound book is held in the lyingpress, while the joints are being formed for attaching the case.
Backing pad
A rubber disc which is secured to a spindle which in turn is attached to a drill or other tool which rotates the spindle. An abrasive disc or polishing disc is secured to the backing pad.
Backing plate

Backing plateBacking plate

  1. The part of a drum brake to which the wheel cylinder(s) and the brake shoes are attached.
  2. A pressed steel plate upon which the brake shoes, wheel cylinder, and anchor pin are mounted.
  1. Printing on the second side of a sheet.
  2. Backing a letterpress printing plate to required height.
The violent reversal of an internal-combustion engine during starting due to a Backfire
  1. The amount of play or clearance between two parts. In the case of gears, it refers to how much one gear can be moved back and forth without moving the gear into which it is meshed.
  2. Mechanical deficiency in a tuning control, with a difference in dial reading between clockwise and counterclockwise rotation.
  3. Property of most regenerative and oscillator circuits, by which oscillation is maintained with a smaller positive feedback than is required for inception.
  4. Movement (if any) of the chain along the pitch line of the sprocket when the direction of chain travel is reversed.
  1. The rear window of a vehicle. Most people call it a rear window and erroneously think of backlight as the taillight.
  2. The light source (often a cold cathode discharge in a flat fluorescent envelope) used in some light-modulating flat panel displays such as those based on LCD
Backlight compensation
(BLC) The opening of the iris to correctly expose a backlit subject which would otherwise be a silhouette
Backlight defogging system
Heated rear window
Backlight heater
Heated rear window
Back lighting
Lighting illuminating the subject from behind, opposite the camera, often to provide rim light or halo effects.
Back lobe
Lobe of polar diagram for antenna, microphone, etc. which points in the reverse direction to that required.
Holding a signal lever partially restored until completion of a predetermined sequence of operation.
The items which follow the main text of a book, i.e., appendices, notes, glossary, bibliography, index. The UK term is end matter
Back observation
An observation made with instrument on station just left. Also called back sight
Back panel
The panel of the body shell set underneath the trunk lid. It is sometimes referred to as the rear valance if the area below the trunk lid consists of only a single panel that extends down to the bottom of the body; in many designs, however, the rear valance is a separate horizontal panel that extends from the rear bumper area downward. The British term is rear panel

British term for Brake backing plate
Back-porch effect
The prolonging of the collector current in a transistor for a brief time after the input signal (particularly if large) has decreased to zero.
Back pressure
  1. The resistance to the flow of exhaust gases through the exhaust system. By rerouting the exhaust gases for noise suppression, a muffler causes back pressure, but a straight pipe alone causes only minimal back pressure. Some engines require back pressure, so that removing the exhaust system will cause internal damage.
  2. Pressure in low side of refrigerating systems; also called suction pressure or low-side pressure.
  3. The pressure opposing the motion of the piston of an engine on its exhaust stroke.
  4. The exhaust pressure of a turbine. Increased by clogged or defective exhaust system.
  5. Pressure against which a fluid or gas is flowing, resulting from friction in lines, restrictions in pipes, valves, pressure in vessel to which fluid is flowing, hydrostatic head, or other impediment that causes resistance to fluid flow.
Back pressure modulated
Back pressure modulated valve
Backpressure Transducer EGR Valve
Back Pressure Transducer Valve
Back-pressure turbine
A steam turbine from which the whole of the exhaust steam, at a suitable pressure, is taken for heating purposes.
Back pressure valve
Backpressure variable transducer
(BVT) a system combining a ported EGR valve and a backpressure variable Transducer to control emissions of NOx
Back projection
  1. Projection of a picture, from film, transparency, or video, on to a translucent screen to be viewed from the opposite side,
  2. A form of motion picture composite photography in which the projected picture forms the background to action taking place in front of it, both being photographed together.
Back rake
In a lathe tool, the inclination of the top surface or face to a plane parallel to the base of the tool.
The back (upright) part of the seat against which your back reclines.
Back scatter
The deflection of radiation or particles by scattering through angles greater than 90° with reference to the original direction of travel.
  1. An air conditioning term which means to rotate a service valve counterclockwise all the way down until the valve is back-seated. When referring to a stem type service valve, the term has a more specific meaning-in the back-seated position, the valve outlet to the system is open and the service port in the valve is closed (its normal operating position).
  2. The seating behind the front passenger and/or driver
Back-seat driver
A person who is not physically in control of the vehicle, but who gives driving instruction to the driver, usually in an obnoxious manner.
Back seating
Fluid opening or closing such as a gauge opening to seat the joint where the valve stem goes through the valve body.
Back sight
Process which maintains synchronization when video recording is stopped and started. The tape being rolled back for roughly one second at the end of a recorded segment then switched into play to compare and synchronize the control track pulses with the incoming synchronization pulses before recording begins again.
Back-step welding
Welding small sections of a joint in a direction opposite the direction that the weld as a whole is progressing.
The structure of a relay which limits the travel of the armature away from the pole-piece or core.
Parallel connection of valves, with the anode of one connected to the cathode of the other, or transistors in parallel in opposite directions, to allow control of AC current without rectification.
Back up
To go in reverse.
Back up alarm
An annoying loud beeping which is repeatedly sounded when a vehicle (usually a large truck) is placed in reverse. It is designed to warn pedestrians behind the vehicle. The British term is reversing warning signal
Back up light
A white light which is located at the rear of the vehicle and is illuminated when the transmission is placed in reverse. The British term is reversing light
Voltage which opposes the current when the current in an inductive circuit changes and the magnetic field cuts the conductors.

Backward busying
Applying busy condition at the incoming end of a trunk or junction (usually during testing or fault-clearance) to indicate at outgoing end that circuit must not be used.
Backward diode
One with characteristic of reverse shape to normal. Also called AU diode or back diode
Backward hold
A method of interlocking the links of a switching chain by originating a locking condition in the final link and extending it successively backwards to each of the preceding links
Backward lead
Backward shift
Movement of the brushes of a commutating machine around the commutator, from the neutral position, and in a direction opposite to that of the rotation of the commutator, so that the brushes short-circuit zero emf conductors when the load current, through armature reaction, results in a rotation of the neutral axis of the air-gap flux. Shifting the brushes in this way reduces sparking on the commutator. Also called backward lead
Backward signaling
Signaling from the called to the calling end of a circuit.
Backward-wave tube
General term for a family of microwave traveling-wave tubes in which energy on a slow-wave circuit or structure, linked closely to the electron beam, flows in the opposite direction to the electrons. They can be used as stable, low-noise amplifiers or as oscillators, as the latter, they can be easily tuned over a wide frequency range by altering he beam voltage.
Backward welding
Water, containing fine fibers, loading and other additives, removed in the forming section of a paper or board-making machine. It is generally re-used within the system or clarified in a saveall to recover suspended matter.
Backyard mechanic
A person, whether qualified or not, who repairs his own vehicle or those of others and works in his own property.
BAC level
Abbreviation for Blood Alcohol Content level
An emblem with a manufacturer’s name and/or logo on a plate to identify a model or component.

Badge engineering
When a manufacturer sells two identical vehicles but the model names are different, he is badge engineering. For example, General Motors may sell a vehicle as a Chevrolet or a Pontiac where the only difference is the model name, logo, and more or less chrome or other minor alterations.
The act of a manufacturer in Badge engineering


  1. An obstruction (e.g., plate, vane, wall) in a tank or container used to slow down or divert the flow of gases, liquids, sound, etc. They are found in the fuel tank, crankcase, muffler, and radiator.
  2. Extended surface surrounding a diaphragm of a sound source (loudspeaker) so that an acoustic short-circuit is prevented.
  3. Any device to impede or divide a fluid flow in a tank to reduce sloshing of liquid.
  4. Plates fitted between cylinders of air-cooled engines to assist cooling.
  5. Internal structure or electrode, with no external connection, used in gas-filled tubes to control the discharge or its decay.
  6. An object placed in an Appliance to change the direction of or retard the flow of gas, air, gas-air mixtures, or flue (exhaust) gases.
  7. A wall or partition inside a liquid tank that inhibits the flow of fluids reducing the slosh effect that liquid tankers experience.
Baffle loudspeaker
An open-diaphragm loudspeaker, in which the radiation of sound power is enhanced by surrounding it with a large plane baffle, generally of wood.
Baffle plate
  1. A metal plate that acts as a Baffle.
  2. A plate used to prevent the movement of a fluid in the direction which it would normally follow, and to direct it into the desired path.
  3. Plate inserted into waveguide to produce change in mode of transmission.
Bag drop
A location where your supplies have been cached. In randonneuring events of 1200 km, you can pre-arrange to have a bag of extra clothes and other supplies waiting for you at a prescribed control (i.e., checkpoint). Also called a drop.
A motorcycle equipped with saddlebags and other touring amenities.
Chevrolet made a bagger in 1964 that is very stylish.
Bag molding
Use of a flexible membrane (the bag) to exert pressure, usually about one atmosphere, on a thermosetting composite laminate or sandwich component while it is curing at ambient temperature in an open mold. Pressure can be generated either by evacuating the inside of the bag (vacuum bag molding) or by pressurizing its outer surface (pressure bag molding).
Bag pump
A form of bellows pump, in which the valved disk taking the place of the bucket is connected to the base of the barrel by an elastic bag, distended at intervals by rings.
The spring-wire loop used to secure the cover on most Master cylinder reservoirs.
Bailey bridge
A temporary bridge made by assembling portable prefabricated panels. A nose is projected over rollers across the stream, being followed by the bridge proper, with roadway. Also used over pontoons.
Baily furnace
An electric-resistance furnace in which the resistance material is crushed coke placed between carbon electrodes; used for heating ingots and bars in rolling mills, for annealing, etc.
A microstructural product formed in steels when cooled from the austenite state at rates or transformation temperatures intermediate between those which form pearlite martensite, i.e., between about 800 and 500° K. It is an acicular structure of supersaturated ferrite containing particles of carbide, the dispersions of the latter depending on the formation temperature. Its hardness is intermediate between that of pearlite and martensite and exhibits mechanical properties similar to those of tempered martensite in a steel of the same carbon content.


A lightweight woollen felt used to cover pool tables and bulletin boards.
A process of drying or curing paint by using heat.
Baked core
A dry sand core baked in the oven to render it hard and to fix its shape.


Baked images
The technique of heating a printing plate (mainly lithographic) to harden the printing image and thus increase the image’s resistance to wear, hence lengthening the run expectancy on the press.
The trademark for a synthetic thermosetting plastic resin used in electrical parts because it is a good insulator. The name comes from its inventor, L. H. Baekeland, 1863-1944.
A term borrowed from food contests where a manufacturer’s design teams compete by displaying their clay model proposals for evaluation.
Preliminary heating of components of a vacuum device to release absorbed gases.
Baking finish
Paint that requires baking in order to dry.
Baking temperature
The temperature at which a varnish or paint must be baked to develop desired final properties of strength and hardness.
  1. The state in which weight is evenly distributed.
  2. The action of applying weights or drilling holes in something to establish even weight distribution so that vibration is reduced.
  3. Adjustment of sources of sound in studios so that the final transmission adheres to an artistic standard.
  4. Said to be obtained in bridge measurements when the various impedances forming the arms of the bridge have been adjusted, so that no current flows through the detector.
Balance bar
The heavy beam by which a canal-lock gate may be swung on its Pintle, and which partially balances the outer end of the gate.
Balance box
A box, filled with heavy material, used to counterbalance the weight of the jib and load of a crane of the cantilever type.
Balance control
A switching device on a stereo radio which adjusts the amount of sound coming from the left and right speakers or from the front and rear speakers.
A crane with two arms, one having counterpoise arrangements to balance the load taken by the other.
Balanced amplifier
One in which there are two identical signal-handling branches operating in phase opposition, with input and output connections balanced to ground.
Balanced-armature pick-up
A pick-up in which the reproducing needle is held by a screw in a magnetic arm, which is pivoted so that its motion diverts magnetic flux from one arm of a magnetic circuit to another, thereby inducing emf in coils on these arms.
Balanced circuit
For AC and DC, a circuit which is balanced to ground potential, i.e., the two conductors are at equal and opposite potentials with reference to ground at every instant.
Balanced crankshaft
A crankshaft with extended reinforcements to form counterbalancing or act as a vibration damper.
Balanced current
A term used, in connection with polyphase circuits, to denote currents which are equal to all the phases. Also applied to DC three-wire systems.
Balanced draft
A system of air-supply to a boiler furnace, in which one fan forces air through the grate, while a second, situated in the uptake, exhausts the flue gases. The pressure in the furnace is thus kept atmospheric, i.e., is balanced.
Balanced draught
A system of air-supply to a boiler furnace, in which one fan forces air through the grate, while a second, situated in the uptake, exhausts the flue gases. The pressure in the furnace is thus kept atmospheric, i.e., is balanced.
Balanced engine
An engine in which all the reciprocating parts such as pistons and connecting rods are adjusted to exactly the same weight.
Balance disc
A disc-shaped device in a centrifugal pump which is attached to the pump shaft. The disc lifts when a force is applied to the underside of the disc allowing pressure to leak past until the axial forces are balanced.
Balanced laminate
Symmetrical laminated material in which the sequence of laminae above the center plane is the mirror image of that below it.
Balanced line
A line in which the impedances to ground of the two conductors are, or are made to be, equal. Also called balanced system
Balanced load
A load connected to a polyphase system, or to a single-phase or DC three-wire system, in such a way that the currents taken from each phase, or from each side of the system, are equal and at equal power factors.
Balanced mixer
A mixer, which may be made of discrete components or formed in stripline or waveguide, in which the local oscillator breakthrough in the output is minimized and certain harmonics suppressed. The contribution of local oscillator noise to the receiver’s overall performance is also reduced by such a mixer.
Balanced modulator
A modulator in which the carrier and modulating signal are combined in such a way that the output contains the two sidebands but not the carrier. Used in color television to modulate subcarriers, and in suppressed-carrier communication systems.
Balanced network
A network arranged for insertion into a Balanced circuit and therefore symmetrical electrically about the mid-points of its input and output pairs of terminals.
Balanced-pair cable
A cable with two conductors forming a loop circuit, the wires being electrically balanced to each other and ground (shield), e.g., an open-wire antenna feeder.
Balanced pedal
In an organ console, the foot-operated plate, pivoted so that it stays in any position, for remote control of the shutter of the chambers in which ranks of organ pipes are situated; it also serves for bringing in all the stops in a graded series.
Balanced protective system
A form of protective system for electric transmission lines and now widely used domestically in which the current entering the line or apparatus is balanced against that leaving it. Any fault, such as a short circuit to ground, upsets this balance and energizes a relay which trips the faulty circuit. Also called differential protective system or colloquially, ground leak relay or ground trip.
Balanced system
Balanced terminator
A two-terminal load in which both terminals present the same impedance to ground.
Balanced voltage
A term used, in connection with polyphase circuits, to denote voltage which are equal to all the phases. Also applied to DC three-wire systems.
Balanced weave
A weave in which the length of free yarn between the intersections is the same as the warp and weft directions and on both sides of the fabric.
Balance gate
A flood gate which revolves about a vertical shaft near its center, and which may be made either self-opening or self-closing as the current sets in or out by giving a preponderating area to one leaf of the gate.
Balance patch
A factory installed patch used to bring a new tire within quality control balance tolerances before distribution and sale. It is placed inside the Tire casing and looks much like a nail hole repair patch.
Balance pipe
A tube which joins two or more carburetors to even out the flow difference.
Balance piston
A device used on polyphase or three-wire systems to equalize the voltages between the phases or the sides of the system, when unbalanced loads are being delivered.

Balancer transformer
An autotransformer connected across the outer conductors of an ac three-wire system, the neutral wire being connected to an intermediate tapping.
Balance shaft
An engine will normally vibrate because of the up-and-down motion of the pistons which turn a crankshaft in one direction. A balance shaft rotates (often in the opposite direction) so that its vibration cancels some of the vibration of the engine. Sometimes an engine will have two balance shafts turning in opposite directions located on either side of the crankshaft.
Balance valve
Balance weight
  1. A lead weight attached to the rim of a wheel.
  2. Small weights threaded on radial arms on the movement of an indicating instrument, so adjusted that the pointer gives the same indication whatever the orientation of the instrument.
  3. A weight used to counterbalance some part of a machine, e.g., weights applied to a crankshaft to minimize or neutralize the inertia forces due to reciprocating and rotating masses of the engine.
  1. Dismantling engine and reassembling it to exact Specifications and tolerances. This process may help to improve engine performance, smoothness, and reliability. Sometimes called Blueprinting.
  2. Keeping wheels in balance.
  3. In color reproduction, control of the levels of the three color components to achieve a satisfactory picture without obvious color bias, esp. in the representation of neutral grey tones.
  4. The process of adjusting a traverse, i.e., applying corrections to the different survey lines and bearings so as to eliminate the closing error.
Balancing antenna
Auxiliary reception antenna which responds to interfering but not to the wanted signals. The interfering signals thus picked up are balanced against those picked up by the main antenna, leaving signals more free from interference.
Balancing machine
A machine for testing the extent to which a revolving part is out of balance, and to determine the weight and position of the masses to be added, or removed, to obtain balance.

Balancing speed
Balancing weight
Bald tire
A tire on which the tread is all worn away. A Slick also has no tread, but this is done deliberately for racing purposes.
The material between two excavations. Also called baulk.


Click image to supersize balk ring
Balk ring
A friction-regulated Pawl or plunger used to make the engagement of gears easier. British spelling is baulk ring
  1. A sphere usually made of metal when used in automotive applications.
  2. A US highway traffic engineering term for a circular traffic light in green, amber, or red.
Ball and nut
Ball-and-nut steering
Ball and ramp
A clutch release mechanism (used in motorcycles) made of two stamped plates with three or four ramps. As one plate is rotated by the clutch cable, the balls climb the ramps, forcing the plates apart. This movement disengages the clutch.
Ball and socket
Ball-and-socket head
Camera mounting allowing universal movement in rotation and tilt before fixing by clamping usually fitted to the top of tripod.
Ball-and-socket joint
A joint between two rods, permitting considerable relative angular movement in any plane. A ball formed on the end of one rod is embraced by a spherical cup on the other. Used in light control systems (e.g., in connecting a pair of bell-cranks which operate in planes at right angles) and in the steering mechanism of motor vehicles, in which both ball and cups are of case-hardened metals. Heavier examples allow a large base plate to be placed under a supporting column in a jack-up pontoon or modified as bridge bearings to allow some articulation.

Ball and spring
  1. Any liquid or solid weight (gravel, stone, or metal) placed in a ship to change the trim, increase the draft, or to regulate the stability.
  2. A layer of broken stone, gravel, or other material deposited above the formation level of road or railway; it serves as foundation for road-metal or permanent-way respectively.
  3. Sandy gravel used as a coarse aggregate in making concrete.
Ballast ignition system
An ignition system which uses a Ballast resistor connected in series with the coil primary winding and which is bypassed when the starter is engaged so that the spark is more efficient under cold weather starting.
The addition of Liquid or Dry weight inside the tire to act as a counterbalance, to increase traction, reduce wheel spin, and dampen out bounce.
Ballast lamp
Normal incandescent lamp used as a ballast resistor, current limiter, alarm, or to stabilize a discharge lamp.
Ballast resistance
A term used in railway signaling to denote the resistance between the two track rails across the Ballast on which the track is laid. If allowed to fall too low, it will have the effect of shunting the signal from a trains’s wheels.
Ballast resistor

  1. A resistor inserted into a circuit to swamp or compensate changes, e.g., those arising through temperature fluctuations. One similarly used to swamp the negative resistance of an arc or gas discharge. Also called ballast tube.
  2. A Resistor constructed of a special type wire, the properties of which tend to increase or decrease the voltage in direct proportion to the heat of the wire.


Ballast tank
Water-tight containers at the bottom or sides of a ship which are filled with seawater for ballasting purpose.
Ballast tube
Ball bearing
An antifriction bearing consisting of an inner and outer Hardened steel Race (or Cage) separated by a series of hardened steel balls.

Ball bearing puller
A tool for removing a ball bearing from a shaft or from a housing.
Ball cage
A circular frame which holds the balls in place in a ball bearing.
Ball check valve
Valve assembly which permits flow of fluid in one direction only.
Ball-ended magnet
A permanent magnet, consisting of a steel wire with a steel ball attached to each end; this gives a close approximation to a unit pole.
Ball end hexagon screwdriver
A tool that looks like an Allen wrench except it has a small ball at the very end. This arrangement allows it to work at various angles.
Ballhead centrifugal
A pair of governor flyweights which are rotated by the engine.
  1. A process that occurs in the cementite constituent of steels on prolonged annealing at 650°C700°C.
  2. The operation of forming balls in a puddling furnace.
Ballistic circuit breaker
A very high-speed circuit breaker, in which the pressure produced by the fusing of an enclosed wire causes interruption of the circuit.
Ballistic galvanometer
A galvanometer with a long swing period; the deflection measures the electric charge in a current pulse or the time integral of a voltage pulse.
Ballistic method
A method of high-grade testing used in electrical engineering, a Ballistic galvanometer being used.
Ballistic pendulum
A heavy block suspended by strings so that its swings are restricted to one plane. If a bullet is fired into the block, the velocity of the bullet may be calculated from a measurement of the angle of swing of the pendulum.
The study of the dynamics of the path taken by an object moving under the influence of a gravitational field.
Ball joint

Ball JointBall Joint

A flexible Joint using a ball and Socket type of construction, used in Steering linkage setups, steering knuckle pivot supports, etc. Their flexibility helps to compensate for the changes in the wheel and steering when turning or hitting a bump on the road. There are usually upper and lower ball joints attached to the upper and lower A-arms. Some have a grease nipple to allow periodic lubrication.

Ball joint rocker arm

Ball Joint Rocker ArmBall Joint Rocker Arm

A Rocker arm used by GM that is mounted upon a ball-shaped device on the end of a Stud instead of being mounted around a shaft.

Ball joint separator
A tool for forcing out ball or tapered joints. One style is shaped like a two-prong fork with a wedge-shaped jaw which is struck with a hammer to separate the joint. Another style uses direct pressure from a screw or screw-activated lever action to split the joint.
Ball joint steering knuckle

Steering KnuckleSteering Knuckle

A steering knuckle that pivots on Ball joints instead of on a kingpin.

An air compartment in the envelope of an aerostat, used to adjust changes of volume in the filler gas.
A general term for aircraft supported by buoyancy and not driven mechanically.

Balloon barrage
An anti-aircraft device consisting of suitably disposed tethered balloons
Balloon former
On rotary presses, an additional former mounted above the others, from which folded webs are gathered to make up the sections of multi-sectioned newspapers or magazines.
Ballooning of yarn
The shape taken up by yarns on the spinning or doubling machines.
Balloon tire
A type of low pressure tire which was first introduced in the 1920s. Its width and height were the same which gave it a rounded shape. This style was used on bicycles as well as automobiles.
A vehicle brand of which the 2LS, 2LT, 2LTS, RH, RH2, and RH3 models with required application are classic cars.
Small, solid glass spheres or beads used as a filler for plastics and to increase reflectivity in paints and printing inks.
Ball-pane hammer
A fitter’s hammer, the head of which has a flat face at one end, and a smaller hemi-spherical face or pane at the other; used chiefly in riveting. Also called Ball pien hammer
Ball pien hammer

Ball Pein HammerBall Pein Hammer

A hammer with two ends on the head. One is round and the other is flat. They are best used for hammering and shaping metal. Also spelled ball peen

Ball peen hammer
A hammer with two ends on the head. One is round and the other is flat. They are best used for hammering and shaping metal. Also spelled ball pien
Ball race
  1. The inner or outer steel ring forming one of the ball tracks of a ball bearing.
  2. Commonly, the complete ball bearing
Ball sizing
Forcing a suitable ball through a hole to finish size it, usually part of a Broach with a series of spherical lands of increasing size arranged along it.
Ball socket
A recessed spherical well for receiving the ball in a Ball joint
Ball steering
Ball track
Ball universal
Ball universal joint
Ball valve
A check valve in which a ball in a tube is used to control the flow of liquid.
Ball worm
Ball worm and nut
Abbreviation for British Airline Pilots Association
Abbreviation for Ballast resistor
Trucker slang for a deer (dead or alive) as in ‘There’s a Bambi on the side at the 43 yardstick.’


A colloquial term for the opening between the top of the steering-wheel rim and the hub through which the driver can see the instrument panel.

Banana bus
A colloquial term for an articulated bus
Banana plug
A single conductor plug which has a spring metal tip, in the shape of a banana. The corresponding socket or jack is termed a banana jack
Banbury mixer
Type of machine used for compounding rubber with vulcanizing ingredients and carbon black.
Bands are like a metal belt which is in the shape of a circle where the two ends are close, but do not meet. They wrap around parts inside the transmission called drums. The drums house the gears and clutches and freewheel until a certain gear needs to be applied. When first gear needs to be applied, the drum for first gear is locked up by the application of the band. By locking up the drum, the gears now drive the wheels rather than freewheel inside the drum.

Band brake
A flexible band wrapped partially around the periphery of a wheel or drum. One end is anchored, and the braking force is applied to the other.

Band chain
Steel tape. More accurate than ordinary chain.
Band clutch
A Friction clutch in which a fabric-lined steel band is contracted on to the periphery of the driving member by engaging gear.
Band conveyor
An endless band passing over, and driven by, horizontal pulleys, thus forming a moving track which is used to convey loose material or small articles. Also called belt conveyor or conveyor belt
Band edge energy
The energy of the edge of the conduction band or valence band in a solid, measured with respect to some convenient reference or else used as the reference level for other energy states.

Band gap
The range of energies which correspond with those values which are forbidden for delocalized states, according to the Band theory of solids. Localized states such as those associated with ionized dopants, impurity atoms, or crystal imperfections exist in the gap. The generation of pairs of electrons and holes requires quanta of at least the energy of the band gap. Direct recombination likewise furnishes quanta with energies at least equal to the band gap.
Band ignitor tube
A valve of mercury pool type in which the control electrode is a metal band outside the glass envelope. Also called capacitron
  1. A structural feature of wrought metallic materials revealed by etching, resulting from microstructural segregates and constitutional differences within the grain structure becoming drawn out in the direction of working.
  2. Defect in videotape recording heads causing visible horizontal bands in the picture.
  3. A plastic or metal strapping used to secure a product to a pallet or skid.
Banding machine
A device used to surround a metal band around freight or secure it to a pallet.
Band-pass filter
Filter which freely passes currents having frequencies within specified nominal limits, and highly attenuates currents with frequencies outside these limits.
Band radio
Band-rejection filter


A narrow endless strip of saw-blading running over and driven by pulleys, as a belt; the strip passes a work table placed normal to the straight part of the blade. The workpiece is forced against the blade and intricate shapes can be cut. Also used for cutting animal carcases in butchery.
Band spectrum
Molecular optical spectrum consisting of numerous very closely spaced lines which are spread through a limited band of frequencies.
  1. Use of a relatively small tuning capacitor in parallel with the main tuning capacitor of a radio receiver, so that fine tuning control can be done with the smaller; useful when the frequency band is crowded.
  2. Mechanical means, like reduction gearing, to achieve the same result.
Band-stop filter
Filter which attenuates signals having frequencies within a certain range or band, while freely passing those outside this range. Also called band-rejection filter
Band theory of solids
For atoms brought together to form a crystalline solid, their outermost electrons are influenced by a periodic potential function, so that their possible energies form bands of allowed values separated by bands of forbidden values (in contrast to the discrete energy states of an isolated atom). These electrons are not localized or associated with any particular atom in the solid. This band structure is of fundamental importance in explaining the properties of metals, semiconductors, and insulators.
  1. The range of audio frequencies that an audio component (radio) can handle.
  2. The width, or spread, of the range of frequencies used for a given purpose, e.g., the width of individual channels allotted to speech or to television transmissions.
  3. The space occupied in the frequency domain by signals of a specified nature, e.g., telephone quality speech, broadcast-quality stereophonic music, television, radar transmission, etc.
B & S
Abbreviation for Bore and Stroke which describes the width of a cylinder hole and the distance that the piston moves each time.
B & S gage
Abbreviation for Brown and Sharpe. A standard measure of wire diameter.
B & S gauge
Abbreviation for Brown and Sharpe. A standard measure of wire diameter.
  1. A colloquial term used to express the cylinders in an engine. Often used with a number such as Six banger.
  2. A British colloquial term for beater (an older, cheaper, well-worn car which is still usable).
  3. One who fakes an accident.
Banger racing
A competition of speed on small racing tracks where older cars are driven as fast as they can go and where bumping other racing cars is permitted (encouraged??).
  1. Besides being a musical instrument, this is a Fitting which is shaped like a banjo. It has round end that is doughnut shaped with a tube coming out from one side. It is usually used to transfer fluid from the center hole of the round end and out the lateral tube.
  2. A drum-shaped central part of an axle casing containing the differential.
Banjo axle
The commonest form of rear-axle casing in which the provision of the differential casing in the center produces a resemblance to a banjo with two necks.
Banjo fitting
A type of hydraulic fitting, shaped like a banjo, through which a hollow bolt passes, allowing fluid transfer from a hydraulic line to a hydraulic component.
Banjo rear axle housing
A rear axle housing from which the differential unit may be removed while the housing remains in place on the vehicle. The housing is solid from side to side. Compare Split rear axle housing
A number of similar pieces of equipment grouped in line and connected, e.g., a bank of engine cylinders, coke ovens, or transformers.

Banked boiler
A boiler furnace in which the rate of combustion is purposely reduced to a very low rate for a period during which the demand for steam has ceased by e.g., covering the fire with slack or fine coal or banking up. Also called banked fire.
Banked fire
  1. The slope of a track from the wall to the Apron, generally measured in the corners.
  2. Angular displacement of the wings of an aircraft about the longitudinal axis, to assist turning. In other words, tipping the plane so that one wing drops while the other rises.
  3. Process of suspending operation in a smelter by feeding fuel into the furnace only until as much metal and slag as possible have been removed, after which all air inlets are closed.
  1. A raised footway inside a bridge parapet.
  2. A ledge on the face of a cutting.


French for bath tub to describe an old vehicle with two rows of seats, no doors, roof, or windshield. Also called touring car


  1. A unit of pressure. One bar equals 100 kilopascals (10 5Pa) or 750.07mm of mercury at 0°C and latitude 45° or about 14.5 psi.
  2. A rod.
  3. A pivoted bar, parallel to a running rail, which being depressed by the wheels of a train, is capable of holding points or giving information about a train’s position
  4. Material of uniform cross-section, which may be cast, rolled, or extruded.
The author and compiler of this dictionary at
Method of magnetic testing in which the sample is in the form of a bar, clamped into a yoke of relatively large cross-section, which forms a low reluctance return path for the flux.
Woven fabric used for coats and suits and made from silk, worsted, or man-made fibers. Characteristic surface appearance arising from the twill or broken-rib weave used in its manufacture.
Barba’s law
Law concerned with the plastic deformation of metal test pieces when strained to fracture in a tensile test; it states that test pieces of identical size deform in a similar manner.
Trucker slang for a low overpass where a large truck might clip its top if the truck’s clearance is higher than the height of the overpass.
An old style streamlined sports car devoted to racing. Distinctive because it had no doors or roof; but had either one or two separate seats. The name was also adopted by Fiat, Maserati, Lamborghini, Ferrari, Alfa Romeo, and other manufactuers of modern sports cars
Bar clamp

Bar ClampBar Clamp

A tool with a stationary head and a sliding foot for clamping purposes.

Bar Code
UPC markings of a series of black bars that identify a product. The code can be scanned to reveal its unique part number for more efficient entry into a computer database.
  1. Something slightly smaller than the specified dimension.
  2. A unit without the attaching hardware
Bare conductor
A conductor not continuously covered with insulation, but supported intermittently by insulators, e.g., bus-bars and overhead lines.
Bare electrodes
Electrodes used in welding that are not coated with a basic slag-forming substance.
Bar ends

Bar EndsBar Ends

Short handlebar Add-on extensions which are attached to the ends of a Mountain bike handlebar to add another riding position.

Bar end shifter

Bar End ShifterBar End Shifter

A bicycle gear shifter that is inserted into each of the ends of a handlebar.

Bare pavement
A road condition where the pavement is visible and substantially free of snow and ice following plowing, scraping, or other means
Bare shell
The shell of a car body in which all parts have been removed including doors, hood, and trunk lid.
A flat-bottomed boat for carrying cargo or bunker oil, usually pulled by tugs.

Barge carriers
Ships designed to carry barges.
Bar generator
Source of pulse signals, giving a bar pattern for testing TV cathode-ray tubes.
Bar keel


Barkhausen effect
The phenomenon of discontinuous changes in the magnetization of a magnetic material while the magnetizing field is smoothly varied. It is the consequence of sudden changes in the domain structure as domain walls overcome various pinning defects and to a lesser extent as domain orientations discontinuously rotate away from preferred crystal areas H. G. Barkhausen (in 1919) detected voltage pulses induced in coils surrounding a magnetic sample as it was magnetized. Analogous ultrasonic emissions are also associated with the magnetization of magnetostrictive materials. The character of Barkhausen emissions is strongly dependent on microstructure and stress.
Barkhause-Kurz oscillator
Oscillator with a triode valve having its grid more positive than the anode. Electrons oscillate about the grid before reaching the anode. Output frequency depends on the transit time of electrons through the tube.
Bar lathe
A small lathe of which the bed consists of a single bar of circular, triangular, or rectangular section.
Barlow lens
A plano-convex lens between the objective and eye-piece of a telescope to increase the magnification by increasing the effective focal length.
Bar magnet
A straight bar-shaped permanent magnet, with a Pole at each end.
Bar mill
A rolling mill with grooved rolls, for producing round, square, or other forms of bar iron of small section.
Unit of effective cross-sectional area of nucleus equal to 10 -28 m². So called because it was pointed out that although one barn is a very small unit of area, to an elementary particle the size of an atom which could capture it is ‘as big as a barn door.’

A small marine growth which attaches vessel’s hull and will reduce its speed.
Barn door
Pair of adjustable flaps on a studio lamp for controlling the light.
A soft cover to reduce noise from a film camera.
  1. Abbreviation for Barometric Pressure
  2. Abbreviation for Barometric pressure sensor.
  3. Abbreviation for Barometric absolute pressure sensor


A carriage where the driver sat in an open front seat while the passengers sat in two rows facing each other within the enclosed cabin much like a small stage coach. Only the rear passenger seat was protected by a folding cover.

A recording Barometer, usually of the aneroid type, in which variations of atmospheric pressure cause movement of a pen which traces a line on a clockwork driven revolving drum.
An instrument used for the measurement of atmospheric pressure. The Mercury barometer is preferable if the highest accuracy of readings is important, but where compactness has to be considered, the Aneroid barometer is often used.


Barometric absolute pressure sensor
(BARO or BP)

  1. A sensor that provides ambient atmospheric pressure information.
  2. Sends a variable voltage signal to the computer which varies in accord with atmospheric pressure, allowing adjustment of the spark advance, EGR flow, and air/fuel ratio as a function of altitude.

Also called a Barometric pressure sensor

Barometric and manifold absolute pressure sensor
(BMAP) A housing containing both BP and MAP sensors.
Barometric corrections
Necessary corrections to the readings of a mercury barometer for index error, temperature, latitude, and height.
Barometric error
The error in the time of swing of a pendulum due to change of air pressure. Though small, it is sometimes avoided in clocks by causing the pendulum to swing in an atmosphere of constant (low) pressure.
Barometric pressure
(BP) The pressure of the atmosphere as read by a barometer. Expressed in millibars (See Bar), the height of a column of mercury, or (SI) in hectopascals (SI units).
Barometric pressure sensor
(BARO or BP) A sensor found in the engine management system which detects the ambient barometric pressure so that precise fuel mixture can be maintained at different altitudes.
Barometric tendency
The rate of change of atmospheric pressure with time. The change of pressure during the previous three hours.
A device which maintains constant atmospheric pressure in a closed volume, e.g., the input and output pressure of fuel metering device of a gas turbine to compensate for atmospheric pressure variation with altitude.
Barrage balloon
A small captive kite balloon, the cable of which is intended to destroy low-flying aircraft.
Barred code
Any dialed code that automatic exchange apparatus is printed to reject by connecting the caller no further than number unobtainable tone.
  1. A hollow, usually cylindrical, machine part, often revolving, sometimes with wall apertures
  2. The Air horn in the carburetor. In particular, it is that part where the Throttle valve is located. If a carburetor has four openings with a throttle valve in each, it is called a four-barrel carburetor.
  3. Another name for the Carburetor barrel, cylinder, Cylinder barrel, Four barrel, Polishing barrel, and Single barrel.
  4. To travel fast as in We barreled down the highway well above the speed limit.
  5. The main cylinder in which molten polymer is prepared for extrusion or injection into molds.
  6. (bbl) A capacity of 42 US gallons (35 imperial gallons or 159.1 litres) frequently used as a unit in the oil industry.
  7. A round drum
Barrel cam
A cylindrical cam with circumferential or end track.
Barrel carburetor
Barrel distortion
Curvilinear distortion of an optical or electronic image in which horizontal and vertical straight lines appear barrel-shaped, bowed outwards. Also called positive distortion.
Barrel etcher
A device usually used to oxidize and thereby strip away hardened photoresist materials during semiconductor processing. In it a batch of wafers is exposed to a low-pressure oxygen plasma.
Barrel hopper
A machine for unscrambling, orienting and feeding small components during a manufacturing process, in which a revolving barrel tumbles the components on to a sloping, vibrating feeding blade.
Barrel Nut
An internally threaded screw with a slotted head.
Barrel plating
Electroplating of many small items by placing them in a perforated barrel revolving in a vat filled with an appropriate plating solution. The barrel is made the cathode in the cell and the articles tumble against each other during rotation, continually touching at different places, and so become uniformly coated with the electrodeposit.
Barrel shape
A drum defect caused by excessive wear at the center of the friction surface.
Barrel tappet
A hollow rocker arm shaped like a barrel.
Barrel temperatures
Temperatures at which an extrusion or injection molding barrel is kept, usually rising to a peak at the nozzle. The range is determined by the polymer type and its melt viscosity.

Barrel Truck

barrel truckBarrel truck

A hand cart (i.e., dolly) designed to move drums or barrels. Also called Barrel wheeler

Barrel-type crankcase
A gasoline-engine crankcase so constructed that the crankshaft must be removed from one end; in more normal construction the crankcase is split.

Barrel wear
A type of brake drum wear in which the center of the friction surface is worn more than the edges
Barrel Wheeler
Iron-wire resistor mounted in a glass bulb containing hydrogen, and having a temperature variation so arranged that the change of resistance ensures that the current in the circuit in which it is connected remains substantially constant over a wide range of voltage. Also called ballast tube
A temporary structure designed to warn vehicles that the road or a portion of the road is no longer usable.

  1. In transformers, the solid insulating material which provides the main insulation, apart from the oil.
  2. The refractory material intended to localize or direct any arc which may arise on the operation of a circuit breaker.
Barrier cream
A special cream which is applied to your hands before working on a greasy engine. When the job is over, you can wash your hands and easily remove the grease stains. Also called invisible glove or silicon glove
Barrier effect
The effect produced by coating metal to shield it from corrosion.
Barrier layer
  1. In semiconductor junctions, the depletion layer
  2. In an optical fiber cable, an intermediate layer of glass between the low refractive index core and the high refractive index cladding.
  3. In general a layer placed so as to inhibit interdiffusion of heat, matter, etc.
Barrier paint
A primer which is used on bare metal to prevent corrosion.
Barring gear
An arrangement for moving heavy electrical plant, using manpower. Rotating machines and transformers are equipped with wheels and movement is possible by inserting crowbars at suitable points and levering the equipment.
Barring motor
A small motor which can be temporarily connected, by a gear or clutch, to a large machine to turn it slowly for adjustment or inspection.
Bar roof
Bar suspension
A method of mounting the motor on an electrically propelled vehicle. One side of the motor is supported on the driving axle and the other side by a spring-suspended bar lying transversely across the truck. Also called yoke suspension.

Bar-type current transformer
A Current transformer in which the primary consists of a single conductor that passes centrally through the iron core upon which the secondary is wound.
Bar winding
An armature winding for an electric machine whose conductors are formed of copper bars.
Bar-wound armature
An armature with large sectioned conductors which are insulated and fixed in position and connected, in contrast with former-wound conductors which are sufficiently thin to be inserted, after shaping in a suitable jig.


Abbreviation for Belt Alternator Starter — a Hybrid vehicle system from GM
  1. The lowest supporting part of an upright member.
  2. The bottom layer or coating in a series of paint coats.
  3. The major ingredient, other than pigments and filler, that make up the non-volatile portion of an adhesive, coating, or sealing compound.
  4. The region between the emitter and collector of a transistor, into which minority carriers are injected. It is essentially the control electrode of the transistor.
  5. The part of an electron tube which has pins, leads, or terminals through which connections are made to the internal electrodes.
  6. The thin flexible support on which a photographic emulsion or magnetic coating is carried.
  7. A layer of specified material of specified thickness placed below the road surface.
Base and clear system
Paint finish which is made up of a colored base coat (usually a metallic finish) and clear lacquer coat.
Base circle
As applied to the camshaft the lowest spot on the cam, the area of the cam directly opposite the lobe or nose. No lift is produced by the base circle. Also called Cam heel
Base coat
The first coat in a paint system. It is either the undercoat or primer or a colored coat which is covered by clear lacquer.
Base gasket
The Gasket directly below the cylinder and between the cylinder and crankcase. Also called cylinder gasket.
Base grease
Base idle
The idle speed determined by the throttle lever setting on the carburetor or throttle body while the idle speed control (ISC) motor, or any other computer-controlled idle speed control device, is fully retracted and disconnected.
Base interest rate
The interest paid on the usage of the vehicle during a lease. It is the cost of a lease before factoring in discounts, fees, and penalties and is not directly comparable to the APR for a loan. Lowering the base interest rate is one of the methods manufacturers use to subsidize leases. The phrase money factor measures the same cost and can be converted into a base interest rate. For example, to convert a money factor of 0.00276 into an approximate base interest rate would multiply the money factor by 24. The result would be 0.0662 or 6.6%.
A fore-and-aft reference line at the upper surface of the flat plate keel at the centerline for flush shell plated vessels. Vertical dimensions are measured from a horizontal plane through the baseline, often called the molded baseline.
Base material
Any material (metal or plastic) which needs to be coated.
Base metal
  1. Metal that is under a coating or that needs to be coated.
  2. Metal to be welded, cut, or brazed.
Base model
The least expensive vehicle with the least amount of features as standard equipment. It has the smallest engine and often manual transmission as well as few power equipment. Base models constitute only a small percentage of the cars sold. Sometimes called a stripper or stripped down unit.
A strong metal plate which is the main support for something.

Base rim
Base rim taper
Base Year
A small studio lamp placed close to or on the camera mounting.
Basic ignition setting
The ignition setting on a non-running engine according to the specifications. After the engine is running, the timing can be set more accurately.
Basic ignition timing
The ignition timing on a non-running engine according to the specifications. After the engine is running, the timing can be set more accurately.
Basic loading
The limiting mechanical load, per unit length, on an overhead line conductor.
Basic price
The price of a vehicle without including any optional accessories, taxes, delivery charges, etc.
Basic process
A steel-making process, either Bessemer, open-hearth, or electric, in which the furnace is lined with a basic refractory, a slag rich in lime being formed, enabling phosphorus to be removed.

Basic six
The group of instruments essential for the flight handling of an aircraft and consisting of the airspeed indicator, vertical speed indicator, altimeter, heading indicator, gyro horizon, and turn and bank indicator.
Basic slag
Furnace slag rich in phosphorus (as calcium phosphate) which, with silicate and lime, is produced in steel making, and ground and sold for agricultural fertilizer.
Basic speed
The speed which an electric motor develops at rated voltage with rated load applied
Basic steel
Steel which has reacted with a basic lining or additive to produce a phosphorus-rich slag and a low-phosphorus steel.
Basic T
A layout of flight instruments standardized for aircraft instrument panels in which four of the essential instrument panels in which four of the essential instruments are arranged in the form of a T. The pitch and roll attitude display is located at the junction of the T flanked by airspeed on the left and attitude on the right. The vertical bar portion of the T is taken up by directional information.
Basic timing
The ignition timing on a non-running engine according to the specifications. After the engine is running, the timing can be set more accurately.
Basic weight
The weight of the structure (wing, body, tail unit, and landing gear) of an aircraft, plus the propulsion system and the airframe services and equipment (mechanical systems, avionics, fuel tanks, and pipes). Includes residual oil and undrainable fuel but no operational equipment or payload.
Basing Point
A specified municipality or location within that municipality that a shipping company determines is on their route. The costs of shipping to that point is laid out in its rate book. However, if the delivery is to a nearby point, the rate is first calculated to the basing point and then a cost is added to the nearby point (if it is farther away) or subtracted (if it is before the basing point).
Basket case
An old car which probably does not run. Often many engine and transmission parts have been removed and are either missing or stored in the trunk or a basket
Basket coil
Coil with criss-cross layers, so designed to minimize self-capacitance.
Bass boost
Amplifier circuit adjustment which regulates the attenuation of the lowest frequencies in the audio scale, usually to offset the progressive loss toward low frequencies.
Bass compensation
Differential attenuation introduced into a sound-reproducing system when the loudness of the reproduction is reduced below normal, to compensate for the diminishing sensitivity of the ear toward the lowest frequencies reproduced.
Bass frequency
A frequency close to the lower limit in an audio-frequency signal or a channel for such, e.g., below 250 Hz.
Something that is irregular, in between, or unusual.
Bastard file

Bastard FileBastard File

A file (a tool) which has a coarse cut (as opposed to a finishing file). It is one cut finer than a coarse file. Files are classed as coarse, second cut, and smooth, from coarsest to finest. Thus, a bastard file is a cut in between a coarse and a second cut. The word bastard functions here in its meaning as irregular or neither coarse nor second cut.

Bastard thread
A screw-thread which does not conform to any recognized standard dimensions.
Bastard title
The fly page before the full title page of a book. Often wrongly called a half-title
  1. A lump or collection of something.
  2. Abbreviation for Battery
  1. A number of things which are produced as a group.
  2. A mixture of natural and synthetic rubber with other material such as fillers, chemicals, and vulcanizing agents in the production of tires.
  3. The mixture of raw materials from which glass is produced in the furnace. A proportion of cullet is either added to the mixture, or placed in the furnace previous to the charge. Also called charge.
Batch box


Batch furnace
A furnace in which the charge is placed and heated to the requisite temperature. The furnace may be maintained at the operating temperature, or heated and cooled with the charge. Distinguished from Continuous furnace
Batch mill
Cylindrical grinding mill into which a quantity of material for precise grinding treatment is charged and worked until finished.
Batch number
A number which may be added to a serial number to identify when the product was manufactured. In this way, when a problem occurs to some products of the same batch, action can be taken to correct or replace others from the same batch.
Batch Picking
A process in a warehouse or parts department where the picker selects several units of each product at one time to fill several orders and then distributes them to each order in a staging or packing location.
Batch process
Any process or manufacture in which operations are completely carried out on specific quantities or a limited number of articles, as contrasted to continuous or mass-production. In semiconductor manufacture, one in which several wafers are treated simultaneously as distinct from stages in which wafers are processed singly.
French term for boat for a boattail shape of the rear of early race cars because it looked like the prow of a boat (upside down).
  1. A tub into which something is immersed.
  2. A liquid solution used for cleaning, plating, or maintaining a specified temperature.
Bath air
Bath air cleaner
Bath lubrication
A method of lubrication in which the part to be lubricated, such as a chain or gearwheel, dips into an oil-bath.
BA thread
Bath Suspension
Bodywork resembling an upside-down bathtub used on the rear of some Triumph motorcycles. It was introduced in 1957 and dropped in the early 1960s. It was also used on Nash cars of the 50’s.
Bathtub combustion chamber
Bathtub chamberClick image to supersize
Bathtub combustion chamber

The volume in the cylinder above the piston that is shaped like an inverted bathtub with the valves in the bottom of the tub. Since all the valves can be arranged in a single row, the valve-operating camshaft and/or rocker gear are simple to design and operate. The long, oval shape of the bathtub controls excessive turbulence, and the flat areas where the piston comes right up to the head surface supply the squish needed to swirl the mixture. The wide cylinders and short piston strokes in modern engines make it possible to use large valves with bathtub heads for efficient gas flow.

  1. Long strips of wood used in the mold loft for fairing lines
  2. Wooden protective strips in cargo holds
Batter level
A form of clinometer for finding the slope of cuttings and embankments
BatteryClick image to supersize

An electrochemical device with one or more cells for producing direct-current electricity by converting chemical energy. A Primary Cell delivers electric current as a result of an electrochemical reaction that is not efficiently reversible, so the cell cannot be recharged efficiently. A Secondary Cell is an electrolytic cell for generating electric energy, in which the cell after being discharged may be restored to a charged condition by sending a current through it in the direction opposite to that of the discharging current. The typical automotive lead-acid battery supplies the source of power for cranking the engine and also provides the necessary electrical energy for the ignition system. In addition, it can (for a limited time) furnish current when the electrical demands of the vehicle exceed the alternator or generator output. Also called the storage battery.

Battery acid
Electrolyte (usually sulfuric acid) in each of the battery cells.
Battery acid tester

Battery TesterBattery Tester

A hydrometer for checking the strength of the acid mixture in each cell of a battery. Fluid is sucked into the instrument by squeezing and releasing the bulb. The scale measures the acid.

Battery and coil ignition system
An ignition system with a battery as the source of primary ignition current.
Battery booster
A motor-generator set used for giving an extra voltage, to enable a battery to be charged from a circuit of a voltage equal to the normal voltage of the battery.
Battery brush

Battery BrushBattery Brush

A specially designed brush set which cleans the outside terminals of the battery post as well as the inside of the battery cable so that good contact is made.

Battery cable
Heavy gage wires used to connect the battery to the vehicle’s electrical system.
Battery cap
Small caps which seal each battery cell.
Battery capacity
The amp-hour capacity.
Battery cell
Individual compartments in a battery which is filled with electrolyte. Six-volt batteries have three cells, 12-volt batteries have six cells.
Battery case
The box made of polypropylene holding several chambers (cells) which have lead plates and filled with electrolyte.
Battery charge
The condition or state of the amount of electricity in a battery.
Battery charge indicator
An instrument which shows the state of charge in a battery.
Battery charger
Battery chargerClick image to supersize
Battery Charger

An electric device which is plugged into an electrical outlet (e.g., 110 volt AC) and connected to the two terminals of the battery to restore the state of charge in the battery. One of leads coming from the charger is red and the other is black. The red lead is clamped on the positive post of the battery while the other is clamped on the frame of the vehicle.

Battery charging
The process of renewing the battery by passing an electric current through the battery in a reverse direction.
Battery charging station
With the advent of electric cars, there needs to be places where their batteries can be recharged periodically — thus is born the battery charging station. Also called a charging point.
Battery clamp
A hold down device which secures the battery from moving around.
Battery coil ignition
High-tension supply for spark plugs in automobiles, in which the interruption of a primary current from a battery induces a high secondary emf in another winding on the same magnetic circuit, the high tension being distributed in synchronism with the contact-breaker in the primary circuit.
Battery compartment
A place in the vehicle where the battery is located. In cars and trucks it may be found under the hood (usually toward the front), under one of the seats, or in the trunk. In motorcycles it is found in the middle of the bike, under the seat.
Battery condition
Battery connector
A plug on battery-powered vehicles to connect the batteries to the Charging station
Battery Council International
A group which makes decisions related to battery composition and disposal.
Battery cover
The top of the Battery case. It has several holes (covered with caps) for access to the battery cells.
Battery cut-out
An automatic switch for disconnecting a battery during its charge, if the voltage of the charging circuit falls below that of the battery.
Battery discharge controller
A device on a vehicle which is driven by an electrical motor. It triggers a warning indicator when the battery power drops below a certain level.
Battery discharge indicator
An instrument on a vehicle which is driven by an electrical motor which indicates the percentage of the maximum charge of the battery.
Battery earth
British term for Battery strap or Ground strap
Battery filler
A device with a long hollow tube with a rubber bulb at one end. It is used for inserting into a container of Battery acid and sucking up the acid, then inserting into the battery cell to fill it. However, motorcycle batteries arrive from the manufacturer with no electrolyte (battery acid). Battery acid comes in a large plastic container with a rubber hose to which a metering clamp is attached. The container is usually placed on a higher shelf so that it is fed into the battery by gravity and regulated by the metering clamp.
Battery fill line
A horizontal line on the side of a translucent battery case which indicates the level to which you fill it with electrolyte. Usually there are two lines indicating a minimum level and maximum level.
Battery fluid
Battery hold down clamp
Battery ignition
Any system where the battery supplies the initial voltage to power the starter motor and fire the spark plugs.
Battery ignition system
Battery is dead
The battery does not have enough electrical power to start the car.
Battery is flat
The battery does not have enough electrical power to start the car.
Battery load tester

Battery Load TesterBattery Load Tester

An instrument which is applied to the terminals of a battery. When first installed, the battery voltage appears on the dial. By pressing a switch, the voltage is channeled through a series of resistors. While a battery may indicates 12 volts or more without a load, it may not meet the amperage for which it is rated when under load.

Battery Manufacturers
Battery master switch
A control which cuts power from the battery to the other components of the vehicle. Used to disable a vehicle so that thieves have a harder time stealing the vehicle.
Battery positive voltage
(B+) A term used to designate positive voltage at or near the battery level.
Battery post
The terminal on a battery to which the cable is attached. Older automobile batteries used a round post which stood up from the top of the battery. To avoid confusion, the positive post has a larger diameter than the negative. On newer batteries the post may or may not be abandoned in favor of a terminal on the side of the battery. On motorcycle batteries, the posts are usually flat with a hole for bolting the cables to them.
Battery powered electrical system
An electrical system having a lead-acid battery as a source of power. The battery is recharged by a charging system using either a generator or alternator.
Battery regulating switch
A switch to regulate the number of cells connected in a series in a battery.
Battery spear
A special form of spike used to connect a voltmeter to the plates of the accumulator cells for battery-testing under load. The voltmeter incorporates a low resistance in shunt which simulates a heavy load on the battery, thus testing its work capability. The heavy current passed for this purpose necessitates special heavy duty battery connectors.
Battery state indicator
Battery strap
  1. A wire cable or braided wire strap to transfer electricity. It can be found between the engine block and the chassis because the engine is isolated from the chassis by rubber mounts. Also called ground strap.
  2. A rubber strap with metal hooks at each end and is used to secure a battery in place, especially on motorcycles.
Battery supported CDI
Capacitive discharge ignition system which uses a battery to supply primary ignition current.
Battery terminal clamp
Battery terminal clamp
Battery terminal
  1. A Battery post on the top of the battery or a lug with a hole on the side of the battery.
  2. The clamp at the end of a battery cable.
Battery tester

Battery TesterBattery Tester

  1. A voltage meter or hydrometer for checking the state of charge of a battery.
  2. An instrument for checking the condition of the battery cells
Battery traction
An electric-traction system in which the current is obtained from batteries (accumulators) on the vehicles.
Battery tray
A metal or plastic on which the battery sits.
Battery vehicle
Baudelot cooler
Heat exchanger in which water flows by gravity over the outside of the tubes or plates.
Baudot code
Code in which five equal-length bits represent one character; sometimes used for teleprinters where one start and one stop element are added to each group of five bits.


Baulk ring
British spelling for Balk ring
  1. Unit of racks designed to accommodate numbers of standard-sized panels, e.g., repeaters or logical units.
  2. An area in the warehouse designated by markings on the columns or floor.
  3. Unit of horizontally extended antenna, e.g., between masts.
Bayonet bulb
Bayonet cap

Bayonet CapBayonet Cap

(BC) A cylindrical base of an electric bulb, usually with two pins projecting on either side, which engage in J-shaped slots to lock the bulb securely in its socket.

Bayonet fitting
An engineering fastening similar to a Bayonet cap

Bayonet holder
Bayonet socket
A socket for receiving a Bayonet cap. It has two slots on either side (usually J-shaped) to accommodate the bulb’s pins.
Bay Storage
A designated area in warehouse or parts department used for storage.
Abbreviation for bottom bracket
A battery once widely used for supplying power for the anode current of valves. Also called anode battery. The UK term is High-tension battery
Abbreviation for Bumper to Back of Cab — the distance from a truck’s front bumper to the back of its cab.
Abbreviation for Before bottom dead center
Abbreviation for Barrel, as in 4-bbl carburetor or as a unit of measurement.
  1. Abbreviation for Bayonet cap
  2. Abbreviation for Blower Control
Abbreviation for Boost-controlled deceleration device
Abbreviation for Battery Council International.
B-class insulation
A class of insulating material which will withstand temperatures up to 130°C
  1. Abbreviation for Body computer module
  2. Abbreviation for Body Control Module
Abbreviation for Bottom dead center
A fifth wheel mounted on one or more axles that are permanently attached and extend off the rear of a semitrailer, most commonly used on flatbeds or tank trailers.
Abbreviation for Breakdown voltage
Beach cruiser
A bicycle that is designed for casual and comfortable road riding and that features a relaxed frame, fat 26-inch tires, a wide saddle, a wide handlebar, and rubber pedals
Beaching gear
Floatable, detachable, temporary trolleys which enable a seaplane to be run on and off the shore or slipway.
Beach marks
Fracture surface markings associated with fatigue crack propagation.

Beach wagon
A woodie station wagon
  1. System of visual lights indicating fixed features, e.g., masts, reefs.
  2. A radio-beacon, which can be of any frequency but is usually very high frequency, and can be omni-directional or of directional beam type.
  3. Vertical fan marker beacons are radio beams used to identify particular spots in control zones and on approach patterns.
  4. A non-directional beacon (NDB) is a transmitter, the bearing of which can be determined only by an aircraft equipped for direction finding.
  1. The portion of a tire which fits onto the rim of the wheel. On a Tubeless tire, the contact of the bead with the rim seals the air into the tire. Bead heel, bead sole, and bead toe form a foot-like shape.
  2. A small ball-like particle used in bead blasting or in some catalytic converters.
  3. In welding, it is the appearance of the finished weld. It describes the neatness of the ripples formed by the metal while it was in a semi liquid state.
  4. A formed, often ornamental molding, usually pliable, sometimes fitted as a sealer like welting between two exterior body panels; e.g., between the fenders and body.
  5. Flexible welting used to trim vehicle upholstery.
Bead base
The part of the tire bead which is in contact with the rim bead seat.
Bead blaster
A cleaning device for removing paint and contaminants from an object.

Bead blasting
A cleaning process which uses glass beads which are forced by air pressure against the object to be cleaned. This system removes paint and contaminants from objects which are awkwardly shaped.
Bead breaker
A device used to remove a tire from its rim by releasing the tension the bead has upon the rim.
The part which keeps the tire on the wheel rim.
Bead core
The ring of steel wires in the bead of the tire. Also called Bead wires
Beaded edge
The edge of a body panel or upholstery panel wrapped around a wire or other stiffening item. Also called Rolled bead
Beaded edge tire
An older form of high-pressure tire with projecting beads.
A power tool for forming beads on the edges of body panels.
Bead expander
A device used in the mounting of tubeless tires to prevent inflation air from escaping and bring the tire beads against the tapered bead seat area (rim).
Bead heel
The portion of the tire bead in contact with the rim flange.
  1. The action of forming a step in the middle of a panel (not at the edge) which creates a shallow indentation to reinforce the panel.
  2. A formed, often ornamental molding, usually pliable, sometimes fitted as a sealer like welting located between two exterior body panels; e.g., between fenders and body.
  3. Welting used to trim car upholstery.
Bead lock
Bead movement
Movement of the bead on the rim caused by improper inflation, excessive loading, improper design, improper seating, or improper rim or tire size. Also called bead rocking.

Bead point
A feathered rubber extension of the bead toe used where a flap is not required; protects the tube from chafing between bead toes and rim base.
Bead seat
The portion of the wheel rim below the rim flange providing radial support to the bead of the tire.

Bead seat mat
A seat cover made of a network of wood beads.
Bead seats
Bead seat taper
Bead seat diameter
The measurement of tire diameter, at the bead heel, where it seats on the rim. It is marked on the tire sidewall following Section width.
Bead separation
A situation where the bead comes off the wheel rim.
Bead tire
Bead toe
The bottom portion of the tire bead in contact with the rim bead seat.
Bead unseating
Shifting of the tire bead from its seat on the wheel rim which often leads to the removal of the tire.

Bead wires
Steel wires wound around the circumference and placed in the beads. Their tension prevents the beads from lifting over the rim flanges. Also called Bead core
Beak iron
  1. The pointed, or horn=shaped, end of a blacksmith’s anvil, used in forging rings, bends, etc.
  2. A T-shaped stake, similarly shaped, fitting in the hardy hole of the anvil. Also called beck iron, bickern, bick iron.
  1. A projection of light. A collimated, or approximately unidirectional, flow of electromagnetic radiation (radio, light, X-rays), or of particles (atoms, electrons, molecules). The angular beam width is defined by the half-intensity points.
  2. A supporting bar. A bar or member which is loaded transversely, predominantly in bending
  3. The width of a ship. Also called breadth.
  4. A wooden or metal cylinder having large flanges at each end. Warp yarns are wound on the beam from cones or cheeses correctly arranged for inserting into the loom or warp-knitting machine. Beams are also used to furnish thread during lace making.
Beam antenna
Generally, any antenna which has focus or direction. Most commonly used to describe short-wave or very high-frequency antennas, rather than microwave antennas which are almost invariably directional.
Beam axle
A rigid or dead axle which supports the non-driven wheels.


Beam compasses
An instrument for describing large arcs. It consists of a beam of wood or metal carrying two beam heads, adjustable for position along the beam, and serving as the marking points of the compasses. Also called trammels
Beam control
Beam-coupling coefficient
The ratio of the ac signal current produced to the DC beam current in beam coupling
Beam current
That portion of the gun current in cathode-ray tube which passes through the aperture in the anode and impinges on the fluorescent screen.
A form of construction used in early steam-engines, now obsolete. The vertical steam-cylinder acted at one end of a pivoted beam, the work load being connected to the other.
Beam-forming electrode
Electrode to which a potential is applied to concentrate the electron stream into one or more beams. Used in beam tetrodes and cathode-ray tubes.
Beam hole
Hole in shield of reactor, or that around a cyclotron, for extracting a beam of neutrons or γ-rays or to insert equipment or samples for irradiation.
Beam headlight
Beam indicator
A light on the instrument panel which comes on when the high beams are activated. Also called High beam indicator

Beam knee
Bracket between a deck beam and frame.
Beam lead
An integrated circuit bonding option for high-frequency applications in which material is etched clear of part of the metallization layer to provide a short beam of metal (usually gold). The chip is then inverted and the beam is bonded direct to conducting tracks.
Beam optimizer
Beam relay
An electromagnetic relay in which the contacts are mounted on a balanced beam with energizing coils acting on each end and tending to tilt it one way or the other.
Beam rider
System in which a guided missile maintains and returns to a course of maximum signal on a radio beam.
Beam setting
Beam splitter
Optical device for dividing a light beam into two or more paths. In particular, a prism system in a camera to produce three color-separation images from a single objective lens.
Beam Suspension
Beam tetrode
Tetrode having an additional pair of plates, normally connected internally to the cathode, so designed as to concentrate the electron beam between the screen grid and anode, and thus reduce secondary emission effects.
Beam unit
  1. To turn, as in the expression, When you get to the corner, bear right.
  2. Trucker slang for a highway patrol police officer named for Smokey the Bear because they both wore similar hats.
Bear bait
Trucker slang for a leader in a group of trucks as in ‘Looks like Swift is the bear bait tonight’ where bear refers to a police officer (i.e., Smokey the Bear).
Bear cave
Trucker slang for a police station on the highway (also called a zoo) as in The bear cave is empty tonight so watch out.
Picture defect in which dark image areas spread into adjacent light areas
Beard protective system
A form of balanced protective system in which the current entering the winding of an alternator is balanced against that leaving it by passing the conductor at the two ends around the core of a single current transformer, in opposite directions, so that there is normally no flux in the transformer core.
The physical medium and set of protocols used to carry useful traffic as opposed to those used merely for the control signals that set up and maintain the link.
  1. The area of a unit in which the contacting surface of a revolving part rests in order to minimize wear and friction between two surfaces.
  2. The horizontal angle between any survey line and a given reference direction
  3. Angle of direction in horizontal plane in degrees from true north, e.g., of an arriving radio wave as determined by a direction-finding system. Also azimuth.
  4. An antifriction reducing device that is usually found between two moving parts. The Babbitt bearings found between the Connecting rod and the crankshaft are lubricated and cushioned with oil, and the front wheel bearings must be repacked with Grease at regular intervals. Bearings can be ball or roller type.
Bearing assembly
When more than one load needs to be supported, several bearings are used making up the bearing assembly. For instance, a crankshaft may have two bearings (one at each end) as well as a few more in the middle.
Bearing attachment
Bearing block
The two halves of metal which encase a bearing.
Bearing cage


Bearing cap
A rigid, semicircular part which encloses and holds the outer shell of a shell bearing.
Bearing clearance
The amount of space left between a shaft and the bearing surface, this space is for lubricating oil to enter.
Bearing cone
  1. A Tapered roller bearing.
  2. The inner race in an adjustable axial or radial ball bearing.
Bearing crush
The additional height which is purposely manufactured into each bearing half to ensure complete contact of the bearing back with the housing bore when the engine is assembled.
Bearing cup
  1. Retainers, held in place by bolts and nuts, that hold the bearings in place. Also called Bearing shell.
  2. The bearing Race that curves around the outside of a ring of Ball bearings and works in conjunction with a Cone.
  3. The outer race for a ball or roller bearing.
Bearing current
A stray current, induced by magnetic flux linking the shaft of an electrical machine, that flows between the shaft and bearings and may injure the bearing surfaces.
Bearing face
The bottom part of a nut or bolt head which clamps down on the surface of the part it is securing.
Bearing housing
The cavity into which the bearing fits.
Bearing knock
The noise created by movement of a part in a loose or worn bearing.
Bearing material
The metal layer which forms the surface of the wear part of the bearing.
Bearing metals
Metals (alloys) used for that part of a bearing which is in contact with the Journal; e.g., bronze or white metal, used on account of their low coefficient of friction when used with a steel shaft.
Bearing pile
A column which is sunk or driven into the ground to support a vertical load by transmitting it to a firm foundation lower down, or by consolidating the soil so that its bearing power is increased. Formerly of timber but now mor usually reinforced concrete or steel.
Bearing preload
Amount of static pressure exerted on a bearing or a set of bearings. The preload is usually adjusted by a threaded collar or shims.
Bearing puller

Bearing pullerBearing puller

A tool used to remove bearings from a shaft by pulling them off. It has two or more arms which circle around the back side of the bearing and a center post which butts up against the end of the shaft. As the center post is screwed down, the arms pull the bearing toward the end of the shaft.

Bearing race
  1. In ball or roller bearings, it is one of the two steel rings on either side of the ball or roller.
  2. The inner or outer ring that provides the smooth, hard contact surface for the balls or rollers in a bearing.
Supports provided to locate a revolving or reciprocating shaft.
Bearing scraper
A small, triangular tool that looks like a file without teeth. Used for deburring and chamfering the edges of camshaft bearings.
Bearing Seals
Bearing separator

Bearing separatorBearing separator

A tool used to separate double bearings or close-fitting gears when a conventional Bearing puller cannot be used

Bearing shell
One of a pair of thin semicircular steel cups lined with an alloy such as copper-lead or lead-indium, which together enclose a shaft or other rotating member, and are held in a circular housing which can be divided into two halves.
Bearing spacer
On a bicycle or motorcycle, a piece of tubing used between the wheel bearing inner races to prevent unwanted bearing preload as the axle is tightened.
Bearing spin
A type of bearing failure in which a lack of lubrication overheats the bearing until it seizes on the shaft, shears its locking lip, and rotates in the housing or block.
Bearing spread
A purposely manufactured small extra distance across the parting faces of the bearing half, in excess of the actual diameter of the housing bore. Thus the diameter is slightly greater than the housing into which a shell bearing is being placed. Thus the bearing is forced into place to reduce its movement.

Bearing support
Bearing surface
  1. The area of the bearing that is in actual contact with the shaft or other supporting member.
  2. The part of a fastener such as the washer face of a nut or under the head of a machine screw that actually comes in contact with the part it fastens.
Bearing tang
A notch or lip on a bearing shell used to correctly locate the bearing during assembly.
Bearing wall
The supporting or abutment wall of a bridge or arch.
Bear in the air
Trucker slang for an overhead highway patrol as in ‘Slow down Roadrunner you got a bear in the air past the next rest area.’
Bear meat
Trucker slang for a speeding truck without a radar detector as in ‘That gearjamming large car is bear meat.’
Bear report
Trucker slang for asking for the location of the cops as in ‘Can I get a bear report there Covenant.’
A vehicle which performs very well.
Periodic variation in the amplitude of a summation wave containing two sinusoidal components of nearly equal frequencies.
  1. An old or collectible vehicle that is in Driveable condition, but looks terrible inside and out, and probably is missing many original parts. Often used to describe a vehicle that is past the easy Restoration stage but still contains many good driving miles. It is also a term for urban combat car and is usually used in conjunction with the word winter, as in winter beater, which is a vehicle that is so far gone, it is sacrificed to the salt covered roads of winter. It is a disposable collectible that is driven until it disintegrates. In other words, it looks as if someone had been beating it for quite a while. British term is Banger.
  2. A device for hitting something.
  3. A vat containing a heavy cylindrical roll (beater roll), fitted with bars, parallel to the Journal, which rotates against a fixed set of bars (bedplate). The paper fibers in suspension in water pass between these bars in preparation for sheet making.
  4. High-speed revolving shaft having arms equipped with blades or pins. These beat out the heavy impurities in matted raw fibers in opening and Scutching processes.
Beat frequency
Generally, the difference frequency produced by the intermodulation of two frequencies. Specifically, the intermediate frequency in a superhet receiver.
Beat-frequency oscillator (BFO)
The frequency changing stage of a superhet radio receiver.
  1. The subjective difference tone when two sound waves of nearly equal frequencies are simultaneously applied to one ear. It appears as a regular increase and decrease of the combined intensity.
  2. Process for partially breaking down the cell-wall structure of cellulose fibers in water before forming paper sheet.
  3. Process for removing heavy impurities from matted, raw natural textile fibers in the opening and Scutching process.
  4. The spare threads available during the weaving of wool to replace missing warp threads in the mending process.
Beating spoon
The process in weaving by which the newly inserted weft thread is pushed against the edge of the woven fabric.


Beauty side of wheel
The side of the wheel that is exposed to the exterior of the vehicle rather than the side that is attached to the axle. Also called Wheel face.
Beaver cloth
Heavy woollen woven overcoating simulating the lustrous nap of the skin of the beaver by milling and raising the fibers, butting them level and laying them in the same direction.
A hinged (usually hydraulic) ramp on the end of a flatbed trailer enabling vehicles or heavy equipment to drive onto the trailer.
Beavertail antenna
An antenna producing a broad, flat, radar beam.
Be back
A prospective buyer who has been in the dealership before, but has returned for more information or is ready to buy.
Bechgaard salt
(TMTSF) 2 X where X is an inorganic anion such as (PF 6 )-, (AlO 4 )-, (ReO 4 -, and TMTSF is the tetramethyl selenium derivative of TTF (tetrathiofulvalene). These salts are organic electrical conductors.


Beck iron


Beck hydrometer
Hydrometer for measuring the relative density of liquids less dense than water. Graduated in degrees Beck, where °Beck=200(1-rel.d.)
Beckmann apparatus
Apparatus used for measuring the freezing and boiling points of solutions.
Beckmann thermometer
A limited range mercury thermometer with a large bulb. It is used to measure small changes of temperature with great precision. Its mean range can be altered by moving mercury from a reservoir in or out of the bulb.
(Bq) SI unit of radioactivity; one becquerel is the activity of a quantity of radioactive material in which one nucleus decays per second. Replaces the curie 1Bq=2.7×10 -11 Ci. It is a very small unit and commonly used with the standard SI prefixes, a gigabecquerel (Gbq or 10 9 Bq) being often needed.
Any flat surface used as a support.

Trucker slang for moving companies as in ‘Bedbuggers on the side of the road.’
The process of accurately fitting a bearing to its shaft by scraping the former until contact occurs uniformly over the surface.
Bedding-in oil
British term for Break-in oil
Bed in
British term for Break-in
  1. A cast-iron or fabricated steel base, to which the frame of an engine or other machine is attached.
  2. The lower part of an engine which rests on the foundation.
Bed X-Tender

Bed X-TenderBed X-Tender

An apparatus attached to a truck bed which allows longer items to be secured in place

  1. Colloquial term for making something stronger.
  2. Colloquial term for modifying or improving something so it will work faster or more efficiently. Similar to Souped up
Colloquial term for BMW.
Colloquial term for BMW.
  1. A machine consisting of a row of wooden or metal hammers, which fall on a roll of damp cloth as it revolves. The operation closes the spaces between the warp and the weft yarns, and imparts a soft glossy finish to cotton and linen.
  2. Colloquial term for the original rear-engined Volkswagen.
Before bottom dead center
(BBDC) As the crankshaft rotates, it brings the piston down to a place just before it reaches Bottom dead center.
Before top dead center
(BTDC) As the crankshaft rotates, it pushes the piston up to a place just before the top of its movement.
Before upper dead center
(BUDC) As the crankshaft rotates, it pushes the piston up to a place just before the top of its movement.
Beginning Inventory
The list of the number of all products and their value which is determined at the beginning of a period.
  1. A device mounted on a bicycle and used to warn pedestrians and other bikes of your approach. A hollow metallic vessel with a flared mouth which, when struck, vibrates with a fundamental frequency determined by parameters such as its mass and dimensions.
  2. A component that is shaped like half a ball or egg.
Bell center punch
A center punch whose point is automatically located centrally on the end of circular work by a sliding hollow conical guide.
Bell chuck
An attachment to a lathe (i.e., chuck) shaped like a bell or cup that is screwed to a mandrel and can grip bits. Also called Cup chuck
Bell-crank lever
A lever consisting of two arms generally at right angles, with a common fulcrum at their junction.
Bell housing

Bell housingBell housing

Sometimes called Clutch housing. The metal covering around the Flywheel and clutch (of a manual transmission) or Torque converter assembly (of an automatic transmission).

Bell metal
High tin bronze, containing up to 30% tin and some zinc and lead. Used in casting bells.
Bell mouth
Bell-shaped air intake attached to some carburetors.
A form of brake drum distortion in which the open edge of the drum has a large diameter than the closed edge.
Said of a hole or bore when its diameter gradually increases toward one or both open ends, the bore profile in section being curved. Usually a manufacturing fault.
  1. A sealed, accordion-type chamber (gas filled or vacuum) which expands and contracts in accordance with temperature changes or provides a seal during movement of parts. Used as an air conditioning control device on many systems.
  2. The flexible connection between parts of a camera or enlarger, necessarily light-tight, to permit delicate adjustments, usually of focusing.
  3. corrugated cylindrical container which moves as pressures change, or provides a seal during movement of parts
Bellows seal
  1. Method of sealing the valve stem. The ends of the sealing material are fastened to the bonnet and to the stem. Seal expands and contracts wit the stem level.
  2. An expanding diaphragm used as a seal between the master cylinder reservoir and the reservoir cover. It prevents air from contacting the fluid, yet it allows the fluid to change in volume.
Bells and whistles
A colloquial term for a myriad of options provided on a vehicle as in the expression, ‘My car isn’t the standard model because it has all the bells and whistles.’
Bell-type furnace
A portable inverted furnace or heated cover operated in conjunction with a series of bases upon which the work is to be heated can be loaded and then left to cool after heat treatment. Used chiefly for bright annealing of non-ferrous metals and bright-hardening of steels.
Belly Bin
Boxes attached under the floor of a trailer which can carry cargo, but more often carry spare parts or dunnage.
Belly Dump
A hopper bottom trailer, both empty their load from underneath via gravity.
A sheetmetal plate attached to the bottom of a vehicle body to protect the engine and its components as well as to provide better aerodynamics.
Belly Trailer
  1. A reinforcing band, normally textile, fiberglass, or steel, which runs around the circumference of a tire and strengthens the tread area.


  2. A circular band which is used to transfer power from one component to another. For instance, a Fan belt is used to transfer power from the engine to the Alternator, Water pump, and air conditioner compressor.
  3. An attaching strap.
Belt Alternator Starter
(BAS) A Hybrid vehicle system from GM
Belt anchor
The point where the end of the seat belt is attached.
Belt anchorage
The point where the end of the seat belt is attached.

Belt conveyor
Belt drive
In order to transmit power from a source to a destination, some kind of connection is needed. A bicycle, for instance, uses a chain drive to transmit the power from pedaling action to the rear wheel. A belt drive uses a leather or rubber belt to transfer power from one pulley to another thus increasing or decreasing the speed of rotation of the driven pulley through mechanical advantage. For instance the alternator is rotated by a belt (sometimes called the fan belt) which is driven by a shaft which is directly attached to the crankshaft. Some motorcycle models (like Harley Davidson and Honda) have a belt drive to transmit power to the rear wheels. Since a belt drive requires no lubrication (in contrast with chain drive) it is one of the cleanest final drive systems.
Belt-drive system
A final-drive system that uses a cogged belt and two sprockets to transmit the power to the rear wheel. The belt performs the same function as a conventional chain.
Belted bias tire
A tire which uses both cross-ply and radial-ply patterns with added belts (such as used on radial-ply tires) on diagonal body plies (as in cross-ply tires). As a result the tire has stiffer sidewalls than tires with just straight radial plies.
Belted piston
A piston with a continuous steel band cast into the Skirt below the rings for controlling skirt Expansion.
Belted radial tire
Belted tire
A tire with a stabilizing belt of two or more plies of steel, fiberglass, etc., running circumferentially around the tire between the carcass and the tread rubber. The carcass can be either radial or bias ply.

Belt end
The part of the seat belt which has the bracket which is attached to the floor pan. Some cars attach this end to the car seat itself.
Belt fork
Two parallel prongs attached at right angles to a sliding rod, used to slide a flat belt from a fast to a loose pulley and vice versa. Also called belt striker.
Belt highway
A ring road. A road enabling traffic to bypass a town.
A general term descriptive of materials from which driving belts are made, e.g., leather, cotton, balata, woven hair, plastics, etc.
Belt line
The horizontal line that runs around the body of the vehicle just below the bottom of the glass panel greenhouse (i.e., windows). The British term is waistline
The horizontal line that runs around the body of the vehicle just below the bottom of the glass panel greenhouse. The British term is waistline
Belt mounting
Belt pulley
Belt retractor
A device which automatically pulls the seat belt back into its reel.
Belt sander

Belt sanderBelt sander

A power sanding tool with a rotating belt of sandpaper

Belt slack
The looseness of a belt (either the drive type belt or a seat belt)
Belt slip
When a drive belt is not as tight as it should be, it will slip on the pulley and thus will not transmit power. If a driven pulley is seized, the belt will also slip.
Belt striker


Belt system
Belt tensioner
A device consisting of an idler pulley which is usually located between the drive and driven pulleys. It can be adjusted to increase the tension on the belt.

Belt transmission
Belt up
A British term for Buckle up
Belt warning light
Belt webbing
Strong fabric material used for seat belts
  1. A workbench.
  2. A test bed for studying or repairing an engine.
  3. Fixed rails with adjustable and slidable supports for a waveguide system.
Bench bleeding
A procedure used to bleed the air from a new or rebuilt master cylinder before installation in a vehicle.
Bench grinder

Bench grinderBench grinder

A power tool mounted on a workbench with one or two grinding wheels

Bench seat
A front seat which runs from the left door to the right door. The alternative is Bucket seats.

Bench test
A determination of the power output of an engine when it is mounted on a test bed. Also it can be checked for oil leaks, fuel consumption, emission levels, etc.
Bench vise

Bench viseBench vise

A vise which is mounted on a workbench

Bench work
  1. Work executed at the bench with hand tools or small machines, as distinct from that done at the machines.
  2. Small molds made on a bench in the foundry.
  1. To form into a curved or angular shape.
  2. A curved length of tubing or conduit used to connect the ends of two adjacent straight lengths which are at an angle to one another.
  3. Alteration of direction of a rigid or flexible waveguide. It is E or minor when electric vector is in plane of arc of bending and H or major when at right angles to this. Also called corner
Bending die
Bending moment
At any transverse section of a beam, the algebraic sum of the moments of all the forces to either side of the section.
Bending moment diagram
Diagram representing the variation of bending moment along a beam. It is a graph of bending moment (y-axis) against distance along the beam axis (x-axis).
Bending pliers
Pliers with flat, smooth jaws used to hold sheet metal in place.
Bending rolls
A large machine used to give curvature to plates. It usually has three rolls with axes arranged in a triangle so that adjusting one relative to the others forms a curve on a strip or sheet of metal passed between them.

Bending Slab
Heavy cast iron perforated thick plate arranged to form a large floor on which frames, etc., are bent.
Bending spring
Coil spring which is placed on inside or outside of tubing to keep it from collapsing while bending it.
Bending strength
The ability of metal to resist bending (i.e., Bending moment). Also called flexural strength.
Bending test
  1. A test made on a beam to determine its deflection and strength under bending load. The most usual forms are symmetrical three-point and symmetrical four-point bending, the advantage of the latter being that a constant bending moment is imposed between the two central loading points. Also called flexural test.
  2. A forge test in which flat bars etc. are bent through 180° as a test of ductility.
Bending wave
Wave observed on thin plates and bars. The motion is perpendicular to the direction of propagation. Important for sound radiation from walls and enclosures.
Bendix drive
Bendix screw
A helical screw on the shaft of a starter motor.
Bendix starter
A starter motor with a Bendix drive

Bendix type starter drive
A self-engaging Starter drive gear, the gear moves into engagement when the starter starts spinning and automatically disengages when the starter stops. Also called Inertia drive
Bend test
Bendy bus
A colloquial term for an articulated bus
  1. Colloquial term for a Recumbent bicycle
  2. The vertical portion of a bridge that supports the beams. A bridge bent is located out of the waterway; a pier is located in the waterway.
Bent Bolt
A cylindrical rod having a thread at one end and the other end bent to some desired conformation; also a bent cylindrical rod having threads at both ends.
BentleyClick image for books on

A vehicle brand of which the 1919-1945 models are classic cars. The 1946-67 models are milestone cars.

Bent-tail carrier
A lathe carrier having a bent shank projection into, and engaged by, a slot in the driving plate or chuck.
A vehicle brand of which the 1925-26, 10/30,11/40, 16/50, and 16/50 Sport models with required application are classic cars.

(C6H6) An aromatic hydrocarbon which is a colorless, volatile, flammable liquid. It is present in small proportion in some crude oils and made commercially from petroleum by the catalytic reforming of naphthenes in petroleum naphtha. Also made from coal in the manufacture of coke. Used as a solvent in the manufacture of detergents, synthetic fibers, petrochemicals, and as a component of high-octane gasoline.
A by-product of manufacture of coke. Sometimes it is used as an engine fuel. Has good anti-knock properties.
A carpet square hand-woven by North Africans from hand-spun yarns from the natural colored wool of local sheep. Commonly misused to describe machine-made carpets considered to have a similar appearance.
Chevrolet Beretta BooksClick image for books on
Chevrolet Beretta

A model of automobile manufactured by the Chevrolet division of General Motors from 1986-96.

Bergstrom’s method
A method of assessing the stresses in concrete pavements with particular reference to aerodrome runways and taxing tracks.
BerlinaClick image for books on

A model of automobile from Alfa-Romeo

  1. A World War I term describing a closed luxury vehicle with small windows. The passengers were able to see out; but it was difficult to see in thus maintaining their privacy
  2. A two-door sedan
  1. A horizontal ledge on the side of an embankment or cutting, to intercept earth rolling down the slopes, or to add strength to the construction. Also called bench
  2. A low earth fill constructed in the path of flowing water to divert its direction, or constructed to act as a counterweight beside the road fill to reduce the risk of foundation failure (buttress).
Berm ditch
A channel cut along a berm to drain off excess water.
Bernoulli’s Theorem
  1. In a stream of liquid, the sum of elevation head, pressure head, and velocity remains constant along any line of flow provided no work is done by or upon liquid on course of its flow; decreases in proportion to energy lost in flow.
  2. The law that for a non-viscous, incompressible fluid in steady flow, the sum of the pressure and kinetic energies per unit volume is constant at any point. It is a fundamental law of fluid mechanics.
  1. A place for a ship
  2. A place to sleep
  3. A bunk
  4. A specified small section of the hull structure


An Italian automobile manufacturer noted for creative design. Usually called Gruppo Bertone. Includes X1/9 (1988).

Compounds of other metals with beryllium
Beryllium bronze
A copper-base alloy containing w.25% of beryllium. Develops great hardness (i.e., 300-400 Brinell) after quenching from 800°C followed by heating to 300°C.
Bessemer converter
Large barrel-shaped tilting furnace, charged while fairly vertical with molten metal, and ‘blown’ by air introduced below through tuyères. Discharged by tilting. Now obsolete but replaced by variety of similar shaped but smaller vessels operating in slightly different ways and using oxygen in place of air.
Bessemer pig iron
Pig iron which has been dephosphorized in Bessemer converter lined with basic refractory material.
Bessemer process
Process in which impurities are removed from molten metal or matte by blowing air through molten charge in Bessemer converter. Used to remove carbon and phosphorus from steel, sulfur and iron from copper matte.
Best selected copper
Metal of a lower purity than high-conductivity copper. Generally contains over 99.75% copper. Compare Casting copper.
Beta brass
Copper-zinc alloys, containing 46-49% zinc, which consists (at room temperature) of the intermediate constituents (or intermetallic compound) known as β.


Beta decay
Radioactive disintegration with the emission of an electron or positron accompanied by an uncharged antineutrino or neutrino. The mass number of the nucleus remains unchanged but the atomic number is increased by one or decreased by one depending on whether an electron or positron is emitted.
Beta detector
A radiation detector specially designed to measure β-radiation.
Beta disintegration
Beta disintegration energy
For electron (βa) emission it is the sum of the energies of the particles, the neutrino and the recoil atom. For positron (β + ) emission there is in addition the energy of the rest masses of two electrons.
Iron in the temperature range 750°C860°C, in which a change from the magnetic (alpha) state to the paramagnetic occurs at about 760°C. With carbon in solution the transition is lowered toward 720°C, and when cooling Recalescence is more marked.
Beta particle
An electron or positron emitted in beta decay from a radioactive isotope. Also called β-particle
Beta radiation
Beta particles emitted from a radioactive source
Beta rays
Streams of Beta particles
Beta-ray spectrometer
Spectrometer which determines the spectral distribution of energies of β-particles from radioactive substances or secondary electrons.
Beta thickness gauge
Instrument measuring thickness, based on absorption and backscattering (reflection) by material or sample being measured of β-particles from a radioactive source.
Said of atoms differing in atomic number by one unit. One atom can be considered as ejecting an electron (beta particle) to produce the other one.
Machine used to accelerate electrons to energies of up to 300MeV in pulsed output. The electrons move in an orbit or constant radius between the poles of an electromagnet, and a rapidly alternating magnetic field provides the means of acceleration.
Beta value
In fusion, the ratio of the outward pressure exerted by the plasma to the inward pressure which the magnetic field is capable of exerting. Also called plasma beta
French, originally for lime concrete, now for any kind of concrete.
Béton armé
French for Reinforced concrete
BET surface area
Surface area of a powder calculated from gas adsorption data, by the method devised by Brunauer, Emmett, and Teller.
Betts process
An electrolytic process for refining lead after drossing. The electrolyte is a solution of lead silica fluoride and hydrofluorsilicic acid, and both contain some gelatine. Impurities are all more noble metals than lead and remain on the anode. Gold and silver are recovered from anode sponge.
Better half
Trucker slang for a husband or wife as in ‘I sure do miss my better half.’
Between duals
Between perpendiculars (BP)
A naval term describing the length between the forward perpendicular and after perpendicular (after side of sternpost)

Between wheel spacer
An obsolete circular metal plate having a bolt hole circle and center bore and fitting between the faces of disc wheels to provide additional dual clearance.
A synchrotron at Berkeley, US, which gives a beam of 6.4 GeV protons.
  1. The angle that one surface makes with another when they are not at right angles.
  2. A small slant, usually describing a flat washer which is square and thicker on one side than the other
  3. The angle between the flanges of a frame or other member.
  4. To chamfer
Bevel differential
A differential which has bevel gears for its main elements. This allows the input and output shafts to be at right angles to one another.

Bevel drive shaft
A shaft with a Bevel gear at one end or both ends. It is used primarily for driving an overhead camshaft.
Bevel gear
  1. A gear shaped like the wide end (frustum) of a Cone, used to transmit motion through an angle. They are found in differentials.
  2. A system of toothed wheels connecting shafts whose axes are at an angle to one another but in the same plane.
Bevel gear drive
A transmission which is used to drive one or more shafts which do not line up with the output shaft. Also called Bevel gear transmission
Bevel gear transmission
A transmission which is used to drive one or more shafts which do not line up with the output shaft. Also called Bevel gear drive
Bevel joint
A piston ring gap in which the two ends of the ring are tapered.
Beverage holder
A circular clip located on the center Console, door panel, or instrument panel which is designed to hold a cup or bottle. Also called Cup holder
  1. The crimped edge of metal that secures the glass face to an instrument. A bezel can be either decorative or functional. Some bezels are threaded and secure switches and control Buttons to the dash, Console, or Steering column.
  2. A small indicator light (e.g., for direction signal lights) on instrument panel.
  3. A grooved ring holding the glass of a watch or an instrument dial.
A type of Passenger car wheel
Abbreviation for Beat-frequency oscillator
Abbreviation for Birmingham gauge
Abbreviation for British Gliding Association
Abbreviation for Background video
B(H) curve
B-H curve
B/H curve
Abbreviation for Bulkhead
B(H) loop
B-H loop
B/H loop
Abbreviation for Brinell hardness number, obtained in the Brinell hardness test. Preferred term is now H B after the hardness number. Obtained by forcing a round steel ball into the surface of the object to be tested under a known load and subsequently measuring the diameter of the indentation so produced.
Abbreviation for Brake horsepower.

Abbreviation for Bimetal heat sensor
  1. The acute angle at which the cords in the tire fabric intersect the circumferential centerline of the finished tire.
  2. The application of a potential difference across, or electric currents through, an electronic device to set an operating condition upon which signals are superimposed.
Bias belted tire

Bias Belted TireBias Belted Tire

A type of tire construction in which there are bias plies as well as a belt of steel or synthetic (rayon, nylon, or fiberglass) cords between the carcass and the tread. The belt Overlaps the bias plies and wraps around the circumference. The cords and belt cross each other at Bias angles.

Bias current
Non-signal current supplied to electrode of semiconductor device, magnetic amplifier, tape recorder, etc. to control operation at optimal working point.
Biased protective system
A modification of a balanced protective system, in which the amount of out-of-balance necessary to produce relay operation is increased as the current in the circuit being protected is increased.
Biased result
In observations, sampling, etc., introduction of a systematic error through some malfunction of instrument or weakness in method used, so that error accumulates in a series of measurements.
Polarization of a recording head in magnetic tape recording, to improve linearity of amplitude response, using DC or using AC much higher than the maximum audio-frequency to be reproduced.
Biasing transformer
A special form of transformer used in one form of biased protective system
Bias ply tire
A tire having two or more carcass plies arranged in a criss-cross manner and diagonally to the beads and travels approximately 1/3 the distance around the circumference before attaching to the other bead. Each cord in the next ply is arranged in the same manner, but in the opposite direction. Also called a conventional tire or cross-ply tire
Bias tire

Bias tireBias tire

A type of tire construction in which the tire cords or plies run diagonally from bead to bead. Generally in passenger cars, there are two plies of fabric. In a P185/80D13 tire, the D indicates a bias-ply tire. Sometimes called a conventional tire.

A leather or vinyl covering for the front of a vehicle.


A draw-off tap for water-supply, consisting of a plug-cock having a downward curved extension for discharge.
A draw-off tap of the kind used for domestic water-supply; closed by screwing down a rubber washered disk on to a seating in the valve body.


Bick iron


  1. Composite materials which occur in and are made by living organisms, such as bone, leather.
  2. Composite materials which replace the function of living tissues or organs in mass, such as carbon fiber/epoxy resin artificial limbs.
Biconical horn
Two flat cones apex to apex, for radiating uniformly in horizontal directions when driven from a co-axial line.
Said of a lens which is convex on both surfaces.


A two-wheel non-motorized vehicle in which the two wheels are not side-by-side but in line. Also called bike. A rider is a cyclist, while a biker is a motorcycle rider.

Bicycle Association
Bicycle carrier

Bicycle carrierBicycle carrier

A device which is attached to the rear bumper or to the roof of a vehicle to carry a bicycle.

Bicycle frame

Bicycle frameBicycle frame

The diamond shaped basic section of a bicycle to which the components are added

Bicycle lock

Bicycle lockBicycle lock

A horseshoe-shaped metal locking device which will reach around a small pole (e.g., parking meter) and the frame of a bicycle.

Bicycle moto cross

  1. A type of racing done on a closed dirt track over obstacles, usually on 20- or 24-inch wheels bikes with one gear.
  2. A type of bicycle used in BMX races
Abbreviation for breakerless inductive discharge ignition system
Bi-directional microphone
Microphone which is most sensitive in both directions along one axis
Bi-directional waveform
Waveform which shows reversal of polarity; a bi-directional pulse generator produces both positive and negative pulses.
Bifilar pendulum
Bifilar resistor
Resistor formed by winding a resistor with a hairpin-shaped length of resistance wire, thus reducing the total inductance.
Bifilar suspension
The suspension of a body by two parallel vertical wires or threads which give a considerable controlling torque.
Bi-fuel Vehicle
A motor vehicle with two separate fuel systems designed to run on either an alternative fuel, gasoline or diesel, using only one fuel at a time (i.e., not a mixture of the fuels). Each fuel is stored in a separate tank. Bi-fuel vehicles are referred to as dual-fuel vehicles in the CAA and EPACT.
Bifurcated rivet
A rivet with a split shank, used for holding together sheets of light material; it is closed by opening and tapping down the two halves of the shank.
Big-block engine
A large V-8 engine produced in the ’60s and ’70s. It typically has a cast-iron block and head and is fed by a carburetor. Contrasts with Small-block engine. Although both engines were of the same displacement, the big-block engine was larger in overall size than the small-block engine. Thus, as vehicles grew smaller and more equipment was stuffed into the engine bay, the small-block engine was favored over its larger brother.
Big Cowl and Chassis Bus Type
A type of bus depicting non-school bus coaches mounted on a truck-based, flat back cowl (medium- or heavy-duty truck hood and fender assembly).
Big end
Big end
  1. The end of the connecting rod which fits around the crankpin.
  2. The part of the connecting rod which is attached to the crankshaft
Big-end bearing
Big-end bearing
Big-end bearingClick image to supersize
Big-end bearing

The bearing in the end of the Connecting rod that attaches to the crankshaft

Big-end bolt
One of the bolts attaching the Big-end cap to the connecting rod.

Big-end cap
The detachable end of the connecting rod which fits on the crankpin.
Big Jim
A colloquial term for a device for opening door locks. It is a flexible metal strip about an inch wide and very thin and has a J-shaped end. It is inserted between the door window and the door frame to trigger the latch.
Big rig
A large truck — usually a tractor-trailer unit.
Big/tall rubber
Trucker slang for 24 inch tires as in ‘I just bought new big rubber for my rig.’
Big three
General Motors, Ford, and Chrysler.
Big Twins
The engines in the larger Harley-Davidson bikes.
A twelve-sided figure. Some nuts and bolt heads have twelve sides.
Having 12 sides.
Bihexagon socket
A tool socket which fits 12-sided nuts and bolts.
A two-wheel vehicle — either a bicycle or a motorcycle.

Bike crossing

Bike crossingBike crossing

A place on the highway (usually marked by a sign) indicating a relatively safe place for a bicycle to cross to the other side. Motorists are advised that slow moving bicycles may be on the road.

Bike lane
A lane in the roadway designated by striping and pavement markings for the preferential or exclusive use of bicyclists.
Bike lock

Bike lockBike lock

A horseshoe-shaped metal locking device which will reach around a small pole (e.g., parking meter) and the frame of a bicycle.

A motorcycle rider. In contrast, a cyclist is a bicycle rider.
Bike Seat
  1. Abbreviation for Bilimportorenes Landsforening (Norway).
  2. Abbreviation for the Association of Swedish Automobile Manufacturers and Wholesalers — BIL deals with matters relating to automotive safety, automobile taxes, environmental protection, distribution, trade policy, traffic policy and Swedish and international regulations
Bilateral impedance
Any electrical or electromechanical device through which power can be transmitted in either direction.
Bilateral slit
A slit used in a spectrometer and consisting of two metal strips whose separation can be accurately adjusted.
Bilateral tolerance
A tolerance with dimensional limits above and below the basic size.
  1. A recess area fitted at the curved section between the bottom and the side into which water drains from holds or other spaces.
  2. The curved part of the shell joining the bottom to the sides.
  3. The space inside meaning #2, at the sides of the cellular double bottom, into which unwanted water drains.
Bilge Blocks
Supporting blocks used under the bilge for support during construction or dry docking.
Bilge bracket
A vertical transverse flat plate welded to the tank top or margin plate and to the frame in the area of the bilge.
Bilge keel
A long longitudinal fin fitted on the curved of a ship at the turn of the bilge to reduce rolling.
Bilge Pump
Pump for removing bilge water
Bilge strake
Shell plates at the bilge area.
Bilge Water
Water in the ship due to leaks, sweat, etc.
Bilge Well
A sump to which bilge water drains.
Billed Weight
The weight shown on a freight bill.
  1. A section of a log split lengthwise as you would make firewood.
  2. A small bar of iron or steel.
  3. Semifinished solid product which has been hot-worked by extrusion, forging, and rolling. Smaller than a Bloom
  4. A piece of timber which has three sides sawn and the fourth left round.
Billet mills
The rolling mills used in reducing steel ingots to billets. Also called billet rolls
Billet rolls
Billet split lens
A device used to produce interference fringes. The two halves of the lens are separated so that two images of a slit source provide the coherent sources.
Bill of lading
(BOL) (BL) (B/L)

  1. The cost or the paperwork describing the cost of a vehicle’s load or freight.
  2. Itemized list of goods contained in a shipment
  3. A contract between the shipper and the carrier that includes freight origin and destination, description, and weight.
Two types of metal bonded into a strip and formed into a coil. Each type of metal has different thermal expansion characteristics, so the coil straightens when heated and coils up when cold. Bimetals are used mainly to open and close choke plates on carbureted vehicle.
Bimetal Coil
A fuse element composed of two different metals, e.g., a copper wire coated with tin or lead.
Bimetal heat sensor
(BHS) A strip (usually coiled) consisting of two metals with different expansion characteristics. Bimetal strips are used in thermostatically controlled devices because they move or bend toward the metal that expands least when heat is applied.
Bimetallic brake drum
A drum with an aluminum outer drum cast around a preformed iron liner.
Bimetallic corrosion
When two different metals are attached to each other, some electrons tend to move from one metal to the other. This action happens especially when there is a little moisture between the two pieces.

Bimetallic sensor
Consists of a thermocouple (an arm made of two dissimilar metals with different rates of thermal expansion) that flexes in accordance with temperature changes. Used as a temperature sensor. Also called Bimetal sensor
Bimetallic strip
Bonded strip composed of two metals with differing thermal expansion coefficients; the strip deflects when one side of the strip expands more than the other. Used e.g., in thermal switches.
Bimetal sensor
A device that consists of a thermocouple, an arm made of two dissimilar metals with different rates of thermal expansion, that flexes in accordance with temperature changes. Used as a temperature sensor. Also called Bimetallic sensor

A pair of plane mirrors slightly inclined to one another. Used for the production of two coherent images in interference experiments.
Colloquial term for BMW
Unit in microphones and vibration detectors in which two piezoelectric plates are cemented together in such a way that application of potential difference causes one to contract and the other to expand, so the combination bends as in a Bimetallic strip
A four-sided structure that is mounted on a pallet. It might have a cover.


Binary counter
Flip-flop or toggle circuit which gives one output pulse for two input pulses, thus dividing by two
Binary frequency shift keying
A digital Modulation scheme in which 1 and 0 are represented by switching the Carrier between two different frequencies. It is 3 dB less resistant to additive white Gaussian noise interference than Binary phase shift keying
Binary phase shift keying
A digital Modulation scheme in which 1 and 0 are represented by reversing the phase of the Carrier. It is 3 dB more resistant to additive white Gaussian Noise interference than Binary frequency shift keying
Binary system
An alloy formed by two metals, this is represented by the binary constitutional diagram for the system. In general, any two-component system.
Binary vapor-engine
A heat-engine using two separate working fluids, generally mercury vapor and steam, for the high- and low-temperature portions of the cycle respectively, thus enabling a large temperature range to be used, with improved thermal efficiency.
Listening with two-ears, the result of which is a sense of directivity of the arrival of a sound wave. Said of a stereophonic system with two channels (matched) applying sound to a pair of ears separately, e.g., by earphones. The effect arises from relative phase delay between wavefronts at each ear.
  1. Component used in the mix of carbon products, organic brake linings, sintered metals, tar macadam, etc. to impart cohesion to the body to be formed. The binder may have cold setting properties, or subsequently be heat-treated to give it permanent properties as part of the body or to remove it by volatilization.
  2. The ingredient in a paint that holds or suspends the Pigmentparticles together.
  3. A glue used to hold the various elements of a brake friction material together


Binder bolt
On a bicycle, the bolt used to fasten a stem inside a Steerer tube or a Seatpost inside a Seat tube. Some are quick-release type.

Binder head
Obsolete term for a pan head screw.
Vehicle brakes.
  1. The rubbing of brake shoes against the drum or of brake pads against the disc.
  2. The strip material turned over along the edge of a carpet or mat.
Binding energy
  1. Energy required to remove a particle from a system
  2. Energy required to overcome forces of cohesion and disperse a solid into constituent atoms.
  3. Of a nucleus, the energy which holds nuclear particles together.


Binding Head
A screw or bolt with a rounded top surface and slightly tapered sides. The bearing surface is flat with annular undercut optional.
Bingham flow
Bingham solid
Material which shows little tendency to flow until a critical stress is reached (e.g., toothpaste or modeling clay). Also called Bingham flow
Bingo cards
Trucker slang for the paper cards that hold trucking permits from different states as in ‘Better get your bingo cards out, they’re checkin’ em at the chicken coop.’
The cluster of instruments and switches mounted in a circular casing on or near the steering column.
A pair of telescopes for use with both eyes simultaneously. Essential components are an objective, an eyepiece and some system of prisms to invert and reverse the image.
Binomial array
A linear array in which the current amplitudes are proportional to the coefficients of a binomial expansion. Such an array has no side lobes.
Biochemical Conversion
The use of enzymes and catalysts to change biological substances chemically to produce energy products. For example, the digestion of organic wastes or sewage by microorganisms to produce methane is a biochemical process.
A product which kills any fungus or microbes that may have contaminated Diesel fuel.
A product which is capable of being decomposed by bacteria into harmless elements without danger to the environment.
  1. Diesel fuel made from animal or vegetable fats.
  2. A biodegradable transportation fuel for use in diesel engines that is produced through transesterification of organically derived oils or fats. Biodiesel is used as a component of diesel fuel. In the future it may be used as a replacement for diesel.
  3. The mono alkyl esters of long chain fatty acids derived from renewable lipid feedstocks, such as vegetable oils and animal fats, for use in compression ignition (diesel) engines. Manufactured by transestrification of the organic feedstock by methanol.
  4. Any liquid biofuel suitable as a diesel fuel substitute or diesel fuel additive or extender. Biodiesel fuels are typically made from oils such as soybeans, rapeseed, or sunflowers, or from animal tallow. Biodiesel can also be made from hydrocarbons derived from agricultural products such as rice hulls.
Liquid fuels and blending components produced from biomass (plant) feedstocks, used primarily for transportation.
Produced by biological processes of living organisms. Note EIA uses the term biogenic to refer only to organic nonfossil material of biological origin.
Biological half-life
Time interval required for half of a quantity of radioactive material absorbed by a living organism to be eliminated naturally.
Biological hole
A cavity within a nuclear reactor in which biological specimens are placed for irradiation experiments.
Renewable organic nonfossil matter such as agricultural crops, crop-waste residues, wood, animal and municipal wastes, aquatic plants; fungal growth, etc., used for the production of energy.
Biomass gas
A medium Btu gas containing methane and carbon dioxide, resulting from the action of microorganisms on organic materials such as a landfill.
Biomass waste
Organic non-fossil material of biological origin that is a byproduct or a discarded product. Biomass waste includes municipal solid waste from biogenic sources, landfill gas, sludge waste, agricultural crop byproducts, straw, and other biomass solids, liquids, and gases; but excludes wood and wood-derived fuels (including black liquor), biofuels feedstock, biodiesel, and fuel ethanol. Note EIA biomass waste data also include energy crops grown specifically for energy production, which would not normally constitute waste.
Biot laws
Laws stating that the rotation produced by optically active media is proportional to the length of path, to the concentration (for solutions) and to the inverse square of the wavelength of the light.
Biot modulus
The heat transfer to a wall by a flowing medium, giving the ratio of heat transfer by convection to that by conduction. Defined as αθ/λ, where α is the heat transfer coefficient, λ is the thermal conductivity of medium, and θ is the characteristic length of apparatus.
Biot-Savart law
Expression for the intensity of magnetic flux density produced at a point a distance from a current-carrying conductor.


Bi-phase shift keying
An aircraft or glider with two main supporting surfaces (two wings on each side) above one another.
Bipolar electrode
An electrode in an electroplating bath not connected to either the anode or cathode. Also called secondary electrode.
Bipolar plates
Conductive plate in a fuel cell stack that acts as an anode for one cell and a cathode for the adjacent cell. The plate may be made of metal or a conductive polymer (which may be a carbon-filled composite). The plate usually incorporates flow channels for the fluid feeds and may also contain conduits for heat transfer.
Bipolar transistor
A transistor that uses both positive and negative charge carriers. Both p-n-p and n-p-n types of bipolar transistor can be manufactured, as discrete devices, or for incorporation into integrated circuits.
Two prisms of very acute angle placed side by side and used as a focusing aid on the screens of cameras.
Bird dog
A person who refers prospective customers to a particular dealership or salesman for a given fee or compensation.
Bird’s beak
In microelectronic fabrication; descriptive of the shape of that part of a silicon dioxide layer grown on a silicon wafer near the edge of a region which is protected from oxidation by a diffusion barrier.
Sending highway freight by air.
Birmingham gauge
(BG) Systems of designating the diameters of rods and wires by numbers. Obsolescent, being replaced by preferred metric dimensions.
Birmingham wire gauge
(BWG) Systems of designating the diameters of rods and wires by numbers. Obsolescent, being replaced by preferred metric dimensions.
Birox resistor
Resistor made from a thick film or bismuth ruthenate fired with a glass; noted for stability.
Bismuth spiral
Flat coil of bismuth wire used in magnetic flux measurements; the change of flux is measured by observing the change in resistance of the bismuth wire, which increases with increasing fields.
Bistable circuit
Valve or transistor circuit which has two stable states which can be decided by input signals, much used in counters and scalers.
Bisynchronous motor
A motor like an ordinary synchronous motor but running at twice synchronous speed.
  1. A tool for boring or cutting which fits into a drill.
  2. The tip of a screwdriver.
Bit adapter
A tool (like a screwdriver) with a hollow socket (instead of the blade) to accept a variety of bits.
  1. A vehicle’s ability to adhere to the road (especially to a racing track).
  2. The ability of a tool to secure itself to a fastener as in I want my wrench to get a good bite on that bolt.
Bit error ratio
The rate at which erroneous Bits are received over a link, expressed as a proportion of the overall bit rate. In good systems the bit error ratio can be less than 1 in 10 9 .
  1. A vertical post used in securing a line
  2. A bollard
Bitter end
The inboard end of a ship’s anchor chain that is secured in the chain locker.
Bitter pattern
A pattern showing boundaries of magnetic domains on the surface of a magnetic material, formed by applying a colloidal suspension of a magnetic powder. The particles accumulate where the domain boundaries intersect the surface.
An elastic cement used instead of paint to protect steel.
A naturally occurring viscous mixture, mainly of hydrocarbons heavier than Pentane, that may contain sulfur compounds and that, in its natural occurring viscous state, is not recoverable at a commercial rate through a well.
Bituminous paint
Black or dark colored tarry paint which contains bitumen. Used for the protection of exposed metal parts.
Flexible bag for transporting fuel, often slung beneath a helicopter.
Abbreviation for British Leyland
Of parts of castings and forgings not finished by machining, the dark coating of iron-oxide retained by the surface.

Black and white checkered flag
A flag which is waved at the finishing line in races to indicate the winner.
Black body
A body which completely absorbs any heat or light radiation falling upon it. A black body maintained at a steady temperature is a full radiator at that temperature, since any black body remains in equilibrium with the radiation reaching and leaving it. Also called complete radiator
Black-body radiation
Radiation that would be radiated from an ideal Black body.
Black-body temperature
The temperature at which a Black body would emit the same radiation as is emitted by a given radiator at a given temperature. The black-body temperature of carbon-arc crater is about 3500°C, whereas its true temperature is about 4000°C
Black book
A popular listings of the current car prices, based on age, condition, and optional equipment; published in the Kelly Black Book.
Black box
  1. A recording device which reveals conditions just prior to a crash.
  2. A control unit. A self-contained unit of electronic circuitry; not necessarily black. It should produce a defined output for a defined input without the operator needing to know its contents. Also called brain box
Black burst
A signal without picture information
Black chromium plating
An electroplating deposit of a black chromium layer for decorative purposes.
Black copper
Impure metal, carrying some iron, lead, and sulfur. Produced from copper ores by blast furnace reduction.
Black crush
Tonal distortion in the picture whereby varying dark tones are all reproduced as black.
Black flag
A flag which is colored black and is waved at a race. It indicates that the driver must return to his pit for consultation. It means that the driver has violated a serious racing rule such as spilling fluid on the track or was speeding on the pit road.
Black flag with orange circle

Black Flag With Orange CircleBlack Flag With Orange Circle

As with the black flag for infractions, the black flag with orange circle means the driver must bring the car to the pits on the next lap. This flag indicates there is a serious mechanical problem with the car that can endanger the driver or others. Ignoring this black flag can bring severe penalties as it represents a dangerous situation.

  1. A vehicle brand of which pre-1948 models are classic cars.
  2. Buick BlackhawkBuick Blackhawk

    A concept car produced by the Buick division of General Motors in 2005

A form of malleable iron, in which the core contains rosettes of graphite which appear as a dark area on fracture surfaces.
Carbonaceous material applied as a powder or wash to the internal surfaces of a mold to protect the sand and improve the finish of the casting. Prepared in a blacking mill.
Blacking a tape
Preparing a blank tape for the recording a black burst signal which lays down the video tracks and control track
Black liquor
A byproduct of the paper production process, alkaline spent liquor, that can be used as a source of energy. Alkaline spent liquor is removed from the digesters in the process of chemically pulping wood. After evaporation, the residual black liquor is burned as a fuel in a recovery furnace that permits the recovery of certain basic chemicals.
Black metal
The structural, supporting inner sheetmetal of a body usually painted black.
Black Orion
Trade name for precursor to carbon fiber.
Black red heat
Temperature at which hot metal is just seen to glow in subdued daylight (about 540°C)
Black sand
A mixture of sand and powdered coal forming the floor of an iron foundry.
Blacksmith hammer

Blacksmith hammerBlacksmith hammer

A special hammer for hitting and shaping heated iron.

Black smoke
Incompletely burned fuel in the exhaust indicating the fuel mixture is too rich.
Black start
A power source’s ability to power up from a cold shut down condition to fully operational status through a dedicated auxiliary power source that is totally independent of external systems.
Tires which do not have any white or red coloring.

Black and white flag

Black and white flagBlack and white flag

The black and white flag is used in some series to indicate unsportsmanlike conduct. This is typically held motionless next to a pit board with the car number on it. The driver may be penalized when this flag is shown

A hollow bag which can be inflated. In some instances, fuel tanks will become rusty inside. A possible cure is to install a bladder. This is done by Flushing out the rust chips, applying an acid solution to remove any oil/gas residue, and Coating the inside with a plastic Compound. When done correctly, this plastic Coating does not dissolve when it comes in contact with gasoline.
  1. A straight narrow flat part like the end of a screwdriver or knife.
  2. The part of a windshield wiper (Blade rubber) which contacts the windshield.
  3. One of the vanes of a rotor or impeller.
  4. The moving part of a knife-switch which carries the current and makes contact with the fixed jaws.
Blade activity factor
The capacity of a propeller blade for absorbing power, expressed as a non-dimensional function of the surface and by the formula Blade Activity formula where R is the diameter, and c is the blade chord at any radius r.
Blade angle
The angle between blade chord and plane of rotation at any radius. It is not constant because of the higher airspeed toward the tip, the incidence being progressively reduced to maintain optimum thrust. Change of blade angle from root to tip is called blade twist.
Blade Compressor
Blade connector
A plain metal tongue for forming electrical connections.
Bladed impeller
A rotating part of a centrifugal pump that has blades or vanes.
Blade judder
See wiper blade judder
Blade loading
The thrust of a helicopter rotor divided by the total area of the blades.
Blade rubber
The rubber strip that fits into the arm of a windshield wiper.
Blade shudder
See wiper blade shudder
Blade twist
  1. The lacquer-coated disk ready for placing on a recording machine for making records with a stylus.
  2. A piece of metal, shaped roughly to the required size, on which finishing processes are carried out.
  3. A fastener where one or two stages of manufacturing have been performed, but the fastener has not been finished.
  4. A door key or ignition key that has not been cut to fit the tumblers of a lock.
  1. Region of fertile material surrounding the core in a breeder reactor in which neutrons coming from the core breed more fissile fuel, e.g., uranium-233 from thorium.
  2. The lithium surrounding a fusion reactor core within which fusion neutrons are slowed down, heat is transferred to a primary coolant and tritium is bred from lithium.
Blank flange
A disk, or solid flange, used to blank off the end of a pipe.
Blank groove
Unmodulated groove on disk recording.
  1. Blocking or disabling a circuit for a required interval of time.
  2. Suppression of the picture information while the scanning spot of a cathode ray tube returns after each line, horizontal blanking, or after each field, vertical blanking, taking place during the blanking interval.
Blanking piece
A flat piece of metal which closes off a tube. Also called a blanking plate
Blanking plate
A flat piece of metal which closes off a tube. Also called a blanking piece
Blanking plug
A rubber stopper for filling in the holes of sheetmetal such as drain holes in the floorpan.
Air under pressure, blown into a furnace.

Blast cleaning
The removal of corrosion, dirt, paint, etc. by a blast of abrasive particles.

Blast freezer
Low-temperature evaporator which uses a fan to force air rapidly over the evaporator surface.
Blast furnace
Vertical shaft furnace into the top of which ore mineral or scrap metal, fuel, and slag-forming rock (Flux) is charged. Air, sometimes oxygen-enriched and pre-heated, is blown through from below and products are separately tapped (slag higher and metal lower). Used to smelt iron ore, copper, lead, zinc, and other minerals.
Blast horn
  1. A marked increase in amplitude distortion due to overloading the capacity of some part of a sound-reproducing system; e.g., attempt to exceed 100% depth of modulation in a radio transmitter, or break of continuity in carbon granules in a carbon transmitter.
  2. The operation of disintegrating rock etc. by boring a hole in it, filling with gunpowder or other explosive charge, and firing it.
Blasting fuse
Compound designed to burn at a regulated speed when closed in a tube, used to ignite detonator or explode blasting charge. Types include safety (slow) and detonating (instantaneous).
Blast main
The main blast air-pipes supplying air to a furnace
Blast pipe
Device located in the smoke-box of a steam locomotive used to improve the draft through the fire-tubes. Exhaust steam passing from the nozzle of the blast pipe reduces smoke-box pressure and induces the draft.
Blatthaller loudspeaker
First electrodynamically driven loudspeaker used for high-quality sound reproduction. It has a flat surface which is large compared to the wavelength of the radiated sound and it generates sound of high intensity.
Blavier’s test
A method of locating a fault on an electric cable; resistance measurements are taken with the far end of the cable free, and again with it grounded.
Temporary survey mark, such as slash on tree trunk, to guide prospector or explorer
BlazerClick image for books on

A model of SUV produced by the Chevrolet division of General Motors from 1969 to 2005

Abbreviation for Backlight compensation
  1. To remove air bubbles from hydraulic lines and components of a system.
  2. To reduce the air pressure in tires that have been run, warmed up, and thus increased from their starting pressure — an action which should be avoided.
Bleed down
The collapse of a hydraulic lifter as oil drains out.
The valve or screw used to vent the air out of a liquid-filled system.

Bleeder jar
A glass or transparent plastic container used to detect the escape of air while bleeding brakes
Bleeder nipple
Bleeder resistor
Resistor placed across secondary of transformer to regulate its response curve, esp. when the transformer is not loaded with a proper terminating resistance. One placed in a power supply or rectifier circuit to control its regulation.
Bleeder screw
  1. A hollow screw used to open a bleeder valve to allow fluid and air bubbles from a system like the brake system during a bleeding process.
  2. A small hollow screw or valve found at drum brake wheel cylinders, in disc brake calipers, and adjacent to the outlet ports of some master cylinders. It is opened to release pressure and bleed air and fluid from the hydraulic system after reconditioning or in the event air has gotten into the system.
Bleeder tank
A container that stores brake fluid under pressure. When connected to the master cylinder, the fluid is forced through the system and facilitates bleeding.
Bleeder tubes
Short curved pieces of tubing used in the bleeding of master cylinders.
Bleeder valve
  1. A valve on a wheel cylinder, caliper, or other hydraulic component that is opened to purge or release air from the hydraulic system.
  2. The device which vents air from the brake system.
Bleeder wrench
A tool used to open bleeder valves
  1. The tapping of air from a gas turbine compressor to prevent surging.
  2. The tapping of air from a gas turbine compressor to feed some other equipment, e.g., cabin pressurization or a de-icing system.
  3. A paint defect in which a constituent in an underlying surface discolors subsequent coatings, prevented by applying a barrier coating.
  4. A method of improving the thermal efficiency of a steam plant by withdrawing a small part of the steam from the higher-pressure stages of a turbine to heat the feed-water.
  5. Removing undesirable entrapped air from a hydraulic (e.g., braking) system.
  6. Diffusion of dye from an photographic image.
  7. In fibers, yarns or fabrics of two or more colors, the running of the darker colors, and consequent staining of the lighter colors; during finishing, washing, or solvent cleaning.
  8. The action of venting air from a liquid-filled (hydraulic) system.
  9. Reducing the air pressure in tires that have been run, warmed up, and thus increased from their starting pressure — an action which should be avoided.
  10. Slowly reducing the pressure of liquid or gas from a system or cylinder by slightly opening a valve
  11. The separation of components of a dried adhesive, coating, or sealer film, resulting in an oil-like stain on the surfaces to be bonded, or on finishes
  12. A lower (older or previous) color coming through a fresh Coat of paint.
Bleeding a system
Remove air bubbles from a brake system, a fuel injection system, or a cooling system so that they won’t impede the flow of liquid through that system.
Bleeding sequence
The order of bleeding brake system components
Bleeding the brakes
This refers to the removal of air from the hydraulic system, bleeder screws are loosened at each wheel cylinder, (one at a time) and brake fluid is forced from the master cylinder through the lines until all air is expelled.
Bleed Line
Bleed Passage
Bleed screw
A screw used to release the air from a system like the brake system.

Bleed valve
  1. A valve with small opening inside which permits a minimum fluid flow when the valve is closed.
  2. The device which vents air from the brake system.
An abbreviation for Blemish tire.
A tire with a slight imperfection in appearance that will not affect tire life or safety. Also called a blem.
A device for mixing two fuel oils to achieve a less viscous and more uniform fuel.
Mixing of two compatible fuels having different properties in order to produce an intermediate fuel

Blending components
Blending plant
A facility that has no refining capability but is either capable of producing finished motor gasoline through mechanical blending or blends oxygenates with motor gasoline.
Abbreviation for Blind Landing Experimental Unit operated by the Royal Aircraft Establishment which developed a fully automatic blind landing system.

Commercial pilot’s license


Blind bore cylinder
A cylinder which does not have a separate, detachable head. The cylinder and head are one unit, like a cup.
Blind counts
A method of inventory count that does not rely on the inventory database’s record of what is supposed to be in stock until after the whole inventory is counted.
Blind flying
The flying of an aircraft by a pilot who, because of darkness or poor visibility, must rely on the indication of instrument.
Blind flying instruments
A group of instruments, often on an individual central panel, essential for Blind flying. Commonly airspeed indicator, altimeter, vertical speed, turn-and-slip, artificial horizon, and directional gyro.

  1. Sprinkling small chippings of stone over a tar-dressed road surface.
  2. Placing a thin layer of concrete over a foundation area before the structural concrete is placed.
Blind quarter
An unusually wide C-pillar enclosing the rear seat area.

Blind rivet
A type of rivet which can be clinched as well as placed by access to one side only of a structure. Usually based on a tubular or semitubular rivet design such as a Pop rivet, Chobert rivet, and Explosive rivet.
Blind Side
Right side of truck and trailer.
Blind spot
  1. An area not visible from the driver’s seat. It is usually the area behind the rear quarter and not visible to the driver either through the windshield, side windows, or mirrors. When approaching another vehicle in a lane beside you, avoid being in its blind spot. Also do a shoulder check before switching lanes to check for vehicles in the blind spot.
  2. Areas around a commercial vehicle that are not visible to the driver either through the windshield, side windows or mirrors.
Bright ornamentation (in chrome or gold plating) on a vehicle’s wheels, grill, moldings, trim and badges in order to give the impression of wealth and status.


A red taillight on a bicycle which has a switch which turns it to a steady light or a flashing (blinking) light

Modification of a loran transmission, so that a fluctuation in display indicates incorrect operation.
Spot on cathode-ray tube screen indicating radar function.
  1. A bubble on a paint surface.
  2. A localized bubble on the surface of a tire, normally caused by a separation between plies or between surface rubber and a ply.
  3. A raised area on the surface of solid metal produced by the emanation of gas from within the metal while it is hot and plastic.
Blister copper
An intermediate product in the manufacture of copper. It is produced in a converter, contains 98.4-99.5% copper, and is subsequently refined to give commercial varieties, e.g., tough pitch, deoxidized copper.
The formation of bubbles on the paint surface.
Blister pack
Transparent, thin sheet of plastic thermoformed to cover product for display purposes. Also called bubble pack.
Blister steel
Wrought-iron bars impregnated with carbon by heating in charcoal. Before 1740 this was the only steel available, but is now obsolete.
  1. Abbreviation for Block Learn Multiplier–a term replaced with Long Term Fuel Trim
  2. Abbreviation for the Bureau of Land Management
Abbreviation for British Leyland Motor Corporation
Bloch band
BlockClick image to supersize
Engine Block
  1. That part of the engine containing the cylinders.
  2. Rectangular, square or cylindrical deck spacer, often identified by its location within a pallet as corner block, end block, edge block, inner block, center block, or middle block.
Block brake
A vehicle brake in which a block of cast-iron is forced against the rim of the revolving wheel, either by hand-power, electromagnetic mechanism, or fluid-pressure acting on a piston.

Block Chain
An alternative name used by some manufacturers for bar-link chain or for certain styles of leaf chain.
Block clutch
A Friction clutch in which friction blocks or shoes are forced inward into the grooved rim of the driving member, or expanded into contact with the internal surface of a drum.
Block coefficient
The ratio of the underwater volume of a ship to the volume of a rectangular block with the same effective lengths, draft and beam.
Block deck
The cylinder head gasket surface.
Blocked impedance
The impedance of the input of a Transducer when the output load is infinite, e.g., when the mechanical system, as in a loudspeaker, is prevented from moving.
Block engine
Blocker ring

Blocker ringBlocker ring

A component in a synchromesh system which contains the internal cone. It separates the collar and gear, and prevents the dogs from engaging until all parts are precisely synchronized. When the shift fork engages the cones, the blocker ring shifts slightly so that its dogs prevent the sleeve from engaging the gear wheel. The shift lever resists any effort to push it into gear. When the speed of all three parts are synchronized, the blocker ring shifts again, allowing the sleeve to move forward and engage the aligned dogs on the blocker ring and gear.

Block heater
A devices which, during very cold weather, keeps the engine warm when the vehicle is not being used — thus making cold starts easier. The free end is plugged into 110 volt AC wall socket. It is especially important for starting diesel engines at very low temperatures.

  1. Cut-off of anode current in a valve because of the application of a high negative voltage to the grid; used in Gating or Blanking.
  2. Tendency of polymer film to adhere to itself, a problem in manufacture. Inhibited with surface coating of an anti-blocking agent.
  3. Wood or metal supports used to secure freight in place when loaded on a trailer.
Blocking capacitor
One in signal path to prevent DC continuity. Also called buffer capacitor
Blocking diode
A semiconductor connected in series with a solar cell or cells and a storage battery to keep the battery from discharging through the cell when there is no output or low output, from the solar cell.
Blocking ring


Block Pallet
A pallet with blocks between the pallet decks or beneath the top deck.
Block sanding
The process of using a wooden block wrapped in sandpaper to sand the material.
Block section
The length of track in a railway system that is limited by stop signals.
Block system
The system of controlling the movements of trains by signals and by independent communication between block posts, where the instruments indicating the position of trains, condition of the block sections, and controlling levers for signals, points, etc. are situated. It is absolute if one train alone is permitted within a block section, and permissive if trains are allowed to follow into a block section already occupied by a train.
Block time
The time elapsed from the moment an aircraft starts to leave its loading point to the moment when it comes to rest. It is an important factor in airline organization and scheduling. Also called chock-to-chock, buoy-to-buoy (seaplanes), flight time.


Blood alcohol content
The amount of alcohol in the bloodstream as a result of drinking liquor.
Blood alcohol level
The amount of alcohol in the bloodstream as a result of drinking liquor.
Blood red heat
Dark red glow from heated metal, in temperature range 550°C630°C
  1. A surface film on rubber, caused by the migration to the surface of sulfur, wax, or other unreacted ingredients of the compound. It may be protective to the tire and detrimental only if appearance is a major factor.
  2. Semifinished metal, rectangular in cross-section and for steel not more than twice as long as it is thick. Compare Billet
  3. Surface film on glass, the thin dielectric layers vacuum deposited on a lens to alter its reflectance properties, hence blooming
  4. The film of sulfites and sulfates formed on glass during the annealing process.
  5. The film on glass caused by weathering. Obsolete.
  1. A formation of an undesired thin surface film or a milky white haze or mist on paintwork. It is caused when paint is applied during humid, cold conditions as moisture is trapped in the wet film.
  2. Treatment of the glass-air surfaces of a lens with a deposit of magnesium fluoride or other substance, which reduces internal reflection and increase light transmission.
  3. Spread of spot on cathode-ray tube phosphor due to excessive beam current.
  4. Coating of dielectric surfaces to reduce reflection of electromagnetic waves.
Blooming mills
The rolling mills used in reducing steel ingots to blooms. Called cogging mills in the UK, and not always distinguished from billet (slab) mills.
  1. To become defective either by leaking or burning through.
  2. In a Bessemer converter, passage of air through molten charge.
Blow back
  1. Because of a sticky valve or the intake valve closing late, some of the air-fuel mixture is blown back through the carburetor.
  2. The return, at low speeds, of some of the induced mixture through the carburetor of a gasoline engine; due to the late closing of the intake valve during compression, or by worn or sticking valves.
The Mixture of fuel-air which escapes past the piston rings and causes fumes that form acid and Sludge in the crankcase and smoking from the oil filer hole. Generally there is a loss of engine power. Most are removed through the PCV system.
The Mixture of fuel-air which is lost past the piston rings and causes fumes that form acid and Sludge in the crankcase and smoking from the oil filer hole. Generally there is a loss of engine power. Most are removed through the PCV system.
  1. The escape of gases between the opening of the exhaust valve and the piston reaching bottom dead center, or in a two-stroke engine between exhaust port opening and transfer port opening.
  2. The difference between the opening and closing pressures of a relief/safety valve.
Blowdown period
In a two-stroke engine, it is the time between the exhaust port opening and the transfer port opening which should be sufficiently long enough to allow time for the cylinder pressure to drop below the crankcase pressure, so that the exhaust gases can be expelled more easily.
  1. Also called a supercharger or turbocharger. This is a pump which forces air into the cylinders at higher than atmospheric pressure. The increased pressure forces more air into the cylinders than what would be drawn in normally. In this way the engine can burn more fuel and thus produce more power. There are two main types of blowers the turbocharger, which uses some of the waste heat energy in the exhaust gases to drive a compressor and pump the air; and the belt-driven or shaft-driven supercharger which uses engine power to pump air.
  2. A fan for an interior heating and ventilating system or even for an air-cooled engine.
  3. A fan used to force air and/or gas under pressure.
  4. A ring-shaped perforated pipe, encircling the top of the blast pipe in the smoke-box, to which steam is supplied while a steam engine is standing, the jets providing sufficient draft to keep the fire going.
Blower fan
An electric motor-driven fan which forces air through the evaporator and duct assembly, then forces the cooled air out of the duct work and circulates it through the vehicle passenger compartment.
Blower motor resistor
A device which regulates fan speed.
Blow gun

Blow gunBlow gun

A paint spray gun with a wide nozzle which is fed by air pressure. It is used to blow out crevices in material that is otherwise hard to reach.

A gas-filled cavity in a solid metal. Usually formed by the trapping of bubbles of gas evolved during solidification, but may also be caused by steam generated at the mold surface, air entrapped by the incoming metal, or gas given off by inflammable mold dressing.
Blowing current
The current (DC or rms) which will cause a fuse link to melt.
Blowing engine
The combined steam-engine or gas-engine and large reciprocating air-blower for supplying air to a blast furnace.
Blowing horn
In early automobiles, a rubber bulb was attached to a long tube which ended in a reed (like a musical reed) attached to an horn shaped something like a bugle. When the bulb was pressed, air was sent down the tube, through the reed, and into the horn to make the noise. Blowing the horn was like blowing a musical horn. In modern vehicles electricity or compressed air causes the horn to blow.
The operation of stopping down a blast furnace.
A British term for Blow torch
Blow molding
Two-stage route for making hollow products, e.g., bottles, surfboards (when filled with foam). Extruded Parison is dropped into the split, female-only tool, and blown to shape by air pressure.
  1. An engine equipped with a turbocharger or supercharger.


  2. An engine which is ruined. Usually the piston is Seized.
Blown casting
Casting spoiled by porosity
Blown engine
An engine which has suffered some internal damage and will need extensive repair or replacement.
Blown flap
A Flap, the efficiency of which is improved by blowing air or other gas over its upper surface to maintain attached airflow even at high angles of deflection.
Blown head gasket
A Gasket that has a break between the opening for the cylinder and an opening for the coolant. The coolant will leak into the combustion chamber. This condition can be diagnosed by a loss in coolant and white smoke out the exhaust.
Blowoff valve

Blowoff ValveBlowoff Valve

A one-way valve that opens to the atmosphere above a certain set pressure to relieve excessive internal pressure buildup; often used with a turbocharger installation to limit Boost pressure to the engine. Also called Pressure-relief valve.

Blow-off valve
Blow out
  • To clean a dirty or blocked pipe by blowing compressed air through it.
  • Sudden tire failure.
A sudden rupturing of tire body, causing complete loss of air pressure which flattens the tire.
A sudden rupturing of tire body, causing complete loss of air pressure which flattens the tire.
Blowout coil
Blowout magnet
A permanent or electromagnet used to extinguish more rapidly the arc (in a switch, etc.) caused by breaking an electric circuit.
A respray of doubtful quality, often poorly prepared and carelessly masked.
Blow pin
Device through which air is blown in final stage of Blow molding. Usually ascends into base of descending Parison
Another term applied to the oxyacetylene torch.
Blow through
A turbocharger system in which the turbocharger blows air through the carburetor(s) or fuel injector(s), i.e., the air and fuel mixing occurs downstream from the turbocharger.
Blow torch

Blow TorchBlow Torch

A tool which is attached to a bottle of flammable gas. The gas is ignited to give an intense flame for brazing and soldering. The British term is blowlamp

Trucker slang for a Martin Truck company’s truck as in ‘Can I get a smokey report there Bluebird.’
Blue billy
The residue left after burning off the sulfur from iron sulfide ores.
Blue book
A listing of the current prices for used cars, based on age, condition, and Optional equipment; published in the Kelly Blue Book. Available at banks, loan offices, libraries, and insurance companies.
Blue brittleness
Embrittlement of medium and high carbon steels during tempering in the range of 205°C315°C, so named because the surface of the steel becomes coated with blue colored oxidation film.
Blue flag

Blue flagBlue flag

The blue or passing flag has different meanings depending on how it is held and whether it is used during practice, qualifying, or racing. Generally when it is held motionless it is an indication to a driver that there is a faster car following closely behind, but not yet close enough for a pass. A waving flag generally indicates that the driver is about to be overtaken and should take care to permit the following vehicle a safe pass. Some drivers resist moving over for an over-taking car when they feel they are racing for position. Controversy can follow the use of the passing flag. Some tracks use a blue flag with a diagonal yellow stripe.



Blueing salts
Caustic solution of sodium nitrate, used hot to produce a blue oxide film on the surface of steel.
Blue metal
Condensed metallic fume resulting from distillation of zinc from its ore concentrates. Blue tint is due to slight surface-oxidation of the fine particles.
Dismantling engine and reassembling it to exact Specifications and tolerances. This process may help to improve engine performance, smoothness, and reliability. Sometimes called Balancing.
Blue smoke
The color of the exhaust which indicates that oil is escaping into the combustion chamber and being burned. It is probably due to worn rings, valve seals, etc.
  1. The blue color that appears on chrome pipes when subject to intense heat. In some cases, it can be removed; but most often it is permanent.
  2. The production of a blue oxide film on polished steel by heating in contact with saltpeter or wood ash, either to form a protective coating, or incidental to annealing
Blunt start
  1. End of a threaded screw which is rounded or coned to facilitate insertion.
  2. The removal of the partial thread at the entering end of thread.
The formation of a whitish or misty appearance on the Finish color of the paint surface.
Abbreviation for Barometric and manifold absolute pressure sensor
Abbreviation for British Motor Corporation
Abbreviation for Brake mean effective pressure. The work accomplished during one engine cycle divided by the engine swept volume. It is essentially the engine torque normalized by the engine displacement. The word brake denotes the actual torque/power available at the engine flywheel as measured on a dynamometer. Thus, BMEP is a measure of the useful power output of the engine.
Abbreviation for ballistic missile early warning system. An over-the-horizon radar system for the detection of intercontinental ballistic missiles, with linked sites in the UK, Alaska, and Greenland.

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A German automobile and motorcycle manufacturer. Abbreviation for Bayerische Motoren Werke. A vehicle brand of which the pre-1948 models 327, 328, 327/328, and 335 are classic cars. The 507 models for 1957-59 are milestone cars. Modern automobile models include the following:

  • 3 Series (1988-2008)
  • 5 Series (1988-2008)
  • 6 Series (1988-2007)
  • 7 Series (1988-2007)
  • 8 Series (1991-97)
  • Alpina B7 (2007)
  • M (2000-02)
  • M3 (1988-06)
  • M5 (1988-2007)
  • M6 (2006-07)
  • X3 (2004-07)
  • X5 (2000-07)
  • Z3 (1996-2002)
  • Z4 (2003-08)
  • Z4 M Series (2006-07)
  • Z8 (2000-03)
BMW roundel

BMW logo

The black, blue, and white BMW checkerboard logo.



Abbreviation for British Nuclear Fuels. Organization involved in uranium enrichment, fabrication of fuel elements, reprocessing of irradiated nuclear fuel and production of plutonium. It also operates experimental reactors.

A printed circuit board.

Board diagnostics
Board of Trade Unit
Obsolete unit of electrical energy, equal to one kilowatt-hour.
Board Spacing
See Deck Board Spacing.
Board Span
See Deck Board Span.
Board test
A test of a printed circuit board.
Trucker slang for a bumpy road as in ‘I don’t run 78 often cause it’s a real boardwalk.’
Boat chock
A cradle or support for a lifeboat.
Boat Deck
A deck on which lifeboats are kept.
The rear of a car body with a tapered V-shaped back end like the upside-down prow of a boat. A common streamline effect used in early race cars, such as the Barchetta and Auburn. Also called Bateau shape


Boat trailer
A trailer specially designed for carrying a boat.
Abbreviation for Break-out box
The custom bikes American riders built after WWII where the owners cut off (i.e., ‘bobbed’) much of the bodywork.
A flanged structure intended for the winding of a coil. Also called spool
Bobbin winding
A transformer winding in which all the turns are arranged on a bobbin instead of in the form of a disk. Generally used for the high-voltage windings of small transformers.

Bobtail truckBobtail truck

  1. A large truck tractor without the trailer.
  2. A Straight truck
A weight used to counterbalance some moving part of a machine.

A British term to describe work that is done poorly or with defective materials.
Bodily harm
Physical injury to a person caused by an accident.
Bodily injury
Physical injury to a person caused by an accident.
  1. The main portion of an automobile. Often it refers just to the outside shell.
  2. The main part of a housing.
  3. The shank of a bolt.
  4. In welding, it refers to the main structural part of a regulator.
  5. A term used in describing the thickness or consistency (viscosity) of an adhesive, coating, or sealer
Body alignment shim

Body ShimBody Shim

A flat piece of metal with a slot used to insert at a bolt location to move a body panel slightly into its proper place.

Body and frame
Body and frame construction
Body assembly
The building up of the automobile body from its various components.
Body builder
A person who builds automobile bodies, i.e., Coachbuilder.
Something that is painted the same color as the body.

Body component
Any structural part that makes up the body of a vehicle.
Body computer module
(BCM) Key element of self-diagnostic system used to control vehicle functions based on monitored inputs.
Body construction
The manufacturer of a vehicle body.
Body diameter
Body file
When patching hole in a body panel and filling it with body putty, a body file, which is a hand tool, is used for smoothing the putty to conform to the contour of the body.

Body filler
A substance (often with the name Bondo®) which is a paste used to fill minor imperfections in a body panel. It hardens and is shaped to fit. It can also be painted to match the rest of the vehicle.
Body flange
A point on the body where two panels overlap, forming a small step.
Body framing
An assembly of the body components.
Body fuel injection
Body glass
The windshield, backlight (rear window), and side windows of a vehicle.
Body hammer
A hammer with a large flat pounding surface for removing dents.

Body housing
In the process of building a vehicle, this is a body shell after everything is welded but before it is painted. Named because the original protective undercoat was white or light yellow.
Body injection
Body jack
A hydraulic tool for pushing or pulling body panels into shape.
Body lead
An alloy of lead and tin which is used to fill dents and seems in a body panel to establish a smooth surface. When heated it flows easily to fill the imperfections.
Body-on restoration
Similar to a frame-off restoration except the shell stays on the frame and components are removed, restored, and replaced one by one thus allowing the owner to drive the vehicle periodically.
Body panel
The sheet metal that forms the outside body pieces.
Body plan
  1. A drawing showing frame lines in elevation.
  2. A drawing showing the forms of the various cross sections, the curvature of the deck lines at the side, and the projections, as straight lines of the waterlines, the buttock lines, transverse elevations and the diagonal lines.
Body putty
A malleable material designed to smooth on dented body areas, upon Hardening, the putty is dressed down and the area painted. Also called Bondo®.
Body rattle
A noise in the bodywork usually cased by loose parts, badly fitting doors, hood, fenders, or trunk lid.
Body repair
The act of bring corroded or damaged panels back to like-new condition
Body roll
The rocking or tilting motion of a vehicle when it goes around the corner.
Body sealer
A tar-like substance which is used to seal joints between panels
Body separator plate
Body shell
The bare skeleton of a vehicle with all the wheels, doors, hood, trunk lid, etc. removed.
Body shop
A service outlet specializing in vehicle body repair work.
Body side molding
A protective stripe along each side of the vehicle running from the leading edge of the front fender, along the door panel(s) to the rear end of the back fender. It may be solid plastic or rubber attached directly to the panels while others are attached to a metal strip which in turn is attached to the panels.
Body spoon
A tool with a flat contoured working surface like a spoon. It is used to slap out dents and is sometimes used in place of a dolly when it is too difficult to reach behind the panel.
Body stripe
A decorative stripe applied to a motorcycle fuel tank or the outside of a car to enhance the appearance. Sometimes model names are also part of the stripes.
Body styling kit
An additional set of bolt-on parts (like spoilers, air dams, fender skirts, laker pipes, wings) which are intended to improve the looks, performance, and efficiency.
Body Sweeps
Long templates (usually made of wood, metal, or plastic) used for laying in different curvatures or radii to a full-sized drawing or clay model when designing a vehicle.
Body tub
The bare body shell (minus the doors, trunk lid, hood, fenders) which is lowered onto the chassis at the time of assembly.
The complete body structure mounted on the chassis of a vehicle with a separate chassis, and the complete sheet metal panel for unibody vehicles.
A hesitation usually experienced when starting out.
A two-axle assembly at the rear of some trailers or tractors. Also called a tandem axle.


  1. An assembly of four wheels on two axles with common suspension, usually on heavy commercial vehicles, trailers, and older Ski-Doos®
  2. Assembly of two or more axles on a large truck, usually a pair in tandem
  3. A small vehicle with a short wheelbase running on rails. Commonly used for the conveyance of coal or ore.
  4. A British term for a four-wheel or six-wheel undercarriage of short wheelbase, which forms a pivoted support at one or both ends of a long rigid vehicle such as a locomotive or coach. Also called bogie truck. The US term is truck

Also spelled bogey

Bogie landing gear
A main landing gear carrying a pair or pairs of wheels in tandem and pivoted at the end of the shock strut or Oleo. This arrangement helps to spread the weight of an aircraft over a larger area and also allows the wheel size to be minimized for easier stowage after retraction.
Bogie truck


Bogie wheel
One of the suspension wheels on an older Ski-Doo®.
The process of change from a liquid to a gas through the application of heat.
  1. Closed container in which a liquid may be heated and vaporized.
  2. One of a wide range of pressure vessels in which water or other fluid is heated and then discharged, e.g., either as hot water for heating or as high-pressure steam for power generation.
  3. A device for generating steam for power, processing, or heating purposes; or hot water for heating purposes or hot water supply. Heat from an external combustion source is transmitted to a fluid contained within the tubes found in the boiler shell. This fluid is delivered to an end-use at a desired pressure, temperature, and quality.
Boiler capacity
The weight of steam, usually expressed in kilograms or pounds per hour, which a boiler can evaporate when steaming at full load output.
Boiler Chocks
Blocks and braces to prevent the movement of boilers.
Boiler compositions
Chemicals introduced into boiler feed-water to inhibit scale-formation and corrosion, or to prevent priming or foaming. Examples are sodium compounds (such as soda ash), organic matter and barium compounds.
Boiler covering


Boiler crowns
The upper rounded places of a boiler of the shell type
Boiler efficiency
The ratio of the heat supplied by a boiler in heating and evaporating the feed-water to the heat supplied to the boiler in the fuel. It may vary from 60 to 90%.
Boiler feed-water
The water pumped into a boiler for conversion into steam, usually consisting of condensed exhaust steam and makeup fresh water treated to remove air and impurities.
Boiler fittings and mountings
Boiler fuel
An energy source to produce heat that is transferred to the boiler vessel in order to generate steam or hot water. Fossil fuel is the primary energy source used to produce heat for boilers.
Boiler, high-pressure
Boiler horsepower
Obsolete term for the equivalent of the heating capacity of 33,475 BTU/hr (9804 watts)
Boilermaker’s hammer
Hammer with ball or straight and cross panes; used for caulking, fullering, and scaling boilers.
Boiler plate
Mild steel plate, generally produced by the open-hearth process; used mainly for the shells and drums of steam-boilers. Latterly steel with a higher yield stress is frequently specified.
Boiler pressure
The pressure at which steam is generated in a boiler. It may vary from little over atmospheric pressure for heating purposes, to 1500 lb-in -2 (10000 kNm -2 ) and over for high-pressure turbines.
Boiler scale
A hard coating, chiefly calcium sulfate, deposited on the surfaces of plates and tubes in contact with the water in a steam boiler. If excessive, it leads to overheating of the metal and ultimate failure.
Boiler setting
The supporting structure on which a boiler rests; usually of brick for land boilers and of steel for marine boilers.
Boiler stays
Screwed rods or tubes provided to support the flat surfaces of a boiler against the bursting effect of internal pressure.
Boiler test
  1. A hydraulic-pressure test applied to check watertightness under pressure greater than the working pressure.
  2. An efficiency test carried out to determine evaporative capacity and the magnitude of losses.
Boiler trial
An efficiency test of a steam boiler, in which the weight of feed water and of fuel burnt are measured, and various sources of loss assessed.
The very rapid conversion of a liquid into vapor by the violent evolution of bubbles. It occurs when the temperature reaches such a value that the saturated vapor pressure of the liquid equals the pressure of the atmosphere.
Boiling point

  1. The exact temperature at which a liquid begins to boil or changes to a gas or vapor (i.e., Vaporizes). The boiling point of a liquid decreases with increasing altitude, and increases with pressurization. The coolant in a modern radiator/coolant system can be as high as 127°C.
  2. The temperature at which a liquid boils when exposed to the atmosphere. Since at the boiling point the saturated vapor pressure of a liquid equals the pressure of the atmosphere, the boiling point varies with pressure; it is usual, therefore, to state its value at the standard pressure of 101.325kNm-2.
  3. The temperature and pressure at which a liquid converts to a vapor. In physics, this point is defined as the temperature at which the vapor pressure of a liquid is equal to the pressure of the atmosphere on the liquid, which is equal to 100°C at sea level (101.3 kPa).
Boiling temperature
Temperature at which a fluid changes from a liquid to a gas.

Boiling-water reactor
(BWR) Light water reactor in which the water is allowed to boil into steam which drives the turbines directly.
The application of retread or repair rubber.
  1. Any short upright post used to prevent vehicle access.
  2. On a quay or vessel, a short post around which ropes are secured for purposes of mooring.


A device for measuring microwave or infrared energy, consisting of a temperature-dependent resistance used in a bridge circuit which gives an indication when incident energy heats the resistor. Used for indication when incident energy heats the resistor. Used for power measurement, standing-wave detectors and infrared search and guidance systems.
  1. A supporting brace.
  2. The act of supporting.
  3. A steel block which supports the lower part of the die in a pressing or punching machine.
  4. The rocking steel frame by which the bogie supports the weight of a locomotive or other rolling stock (i.e., railway car).


A securing device upon which a nut is threaded. It usually has a nut-type head. It is usually measured not so much by the size of the wrench required to secure the bolt; but by the diameter of the threads, the thread pitch, the length of the bolt under the head, and the strength of the bolt. A bolt is similar to a machine screw except that a bolt is usually secured with a wrench instead of a screwdriver.

Bolt and nut
A pair of objects with matching screw threads. When either the bolt or the nut is turned, it moves with great force. Often used as fixing devices. The nut is the circular piece that looks like a ring with threads on the inside hole. The bolt is the shaft with threads.

Bolt Blank
A headed rod or bar intended for a subsequent threading operation.
Bolt body
The blank portion of the bolt or screw which is between the thread and the head.
Bolt Circle Diameter
Bolt cutter

Bolt cutterBolt cutter

A tool for severing a bolt when normally unscrewing a nut from the bolt is impossible or time-consuming.

Bolt End
A headless rod threaded at one end and assembled with a square nut, designed to be welded or otherwise fastened to a part or structure.
Bolt hole
The hole in metal through which a bolt must be inserted or screwed in place.

Bolt hole circle
Bolt mains
Bolt-making machine
A machine which forges bolts by forming a head on a round bar.
Accessories which are easily secured to an automobile with just a few bolts rather than having to be welded in place. Usually done by the owner.
Bolt-on fender
A fender which is secured with bolts rather than being welded in place.
Bolt-on goodies
Accessories which are easily secured to an automobile, but are often for show rather than function.
Bolt-on kit
A group of parts available in one package which the owner can attach himself.
Bolt-on wing
British term for Bolt-on fender
A vehicle which is in very poor shape, ‘The car is a bomb and not worth a nickel.’ In contrast, it can also mean a vehicle which has great acceleration, ‘The car flew down the track like a bomb.’
Process of directing a beam of neutrons or high-energy charged particles onto a target material in order to produce nuclear reactions.
Bomb calorimeter
An apparatus used for determining the calorific values of solid or liquid fuels. The bomb consists of a thick-walled, highly polished, steel vessel in which a weighed quantity of the fuel is electrically ignited in an atmosphere of compressed oxygen. The bomb is immersed in a known volume of water to which the combustion heat is transferred, and from the rise of temperature of which the calorific value is calculated.
Bomb sampler
Device for obtaining samples of dispersed particles at predetermined depths within a suspension, consisting of a closed cylindrical vessel with an automatic valve which opens when an extension tube hits the bottom of the suspension container. The sampler fills with suspension and then closes when the vessel is lifted.
  1. A state of adhesion.
  2. The act of connecting two components by means of a glue or adhesive or to cause them to adhere
  3. The junction of the weld metal and the base metal
  4. The grip exerted by one material on another.
  5. The attachment between two surfaces that have been joined.
  6. The adhesion between concrete and its reinforcing steel, due partly to the shrinkage of the concrete in setting and partly to the natural adhesion between the surface particles of steel and concrete.
  7. Link between atoms, considered to be electrical and arising from the distribution of electrons around the nuclei of bonded atoms.
  8. The adherence of snow or ice to the road surface, creating a composite that is stronger than the snow or ice itself
Bonded abrasive
A grinding part which is made of very hard particles which have been glued together to form a wheel, bar, rod, or cone used to wear down or smooth metal.
Bonded brake lining
Brake lining that is attached to the brake shoe by an adhesive rather than by Rivets.
Bonded lining
  1. Brake lining cemented to shoes or bands with high-temperature adhesive and cured under pressure and heat resulting in the elimination for the need for attaching rivets.
  2. A lining which attaches to the Lining table or backing plate with a high-temperature adhesive cured under heat and pressure.
Bonded Warehouse
  1. A government approved storage center and under bond or guarantee for observance of revenue laws.
  2. A storage center for goods waiting until duty is paid or are released in some other proper manner.
Bonded wire
Enameled insulated wire coated with thin plastic; after forming a coil, it is heated by a current or in an oven or both for the plastic to set and the coil to attain a solid permanent form.
  1. The electrical interconnection of metallic parts of an aircraft normally at ground potential for the safe distribution of electrical charges and currents. Protects against charges due to precipitation, static and electrostatic induction due to lightning strikes. Reduces interference and provides a low-resistance electrical return path for current in ground-return systems.
  2. Joining structural parts by adhesive. May be performed at high temperature and pressure.
  3. An electrical connection between adjacent lengths of armoring or across a joint.
  4. The interactions between individual atoms and molecules.
Bonding agent
  1. A material which provides adhesion.
  2. The cement used to secure Bonded linings to a brake shoe.
Bonding clip
A clip used in wiring systems to make connection between the grounded metal sheath of different parts of the wiring, in order to ensure continuity of the sheath
Bonding method
A procedure of joining two components with adhesive.
Bonding range
The time during which a satisfactory bond can be made. It is usually expressed in two numbers, the first number being the time in minutes one must wait after applying adhesive before trying to bond the surfaces, and the latter number being the longest drying period within which satisfactory bonds can be made, usually ten to 30 minutes after applying the adhesive.
Bond length
The minimum length of reinforcing bar required to be embedded in concrete to ensure that the bond develops the full stress in the bar.
A body putty manufactured by 3M
Bond strength
  1. The force or strength necessary to break a bond between two adhering surfaces or materials.
  2. The intermolecular forces which hold matter together, particularly closely continguous surfaces of neighboring media, e.g., liquid in contact with a solid.

Also called Adhesion.



Bone line
A hard, raised longitudinal peak in the sheetmetal, usually along the side of the car body and sharper and higher than a character line
A survey term describing the process of locating and driving in pegs so that they are in line and have their tops also in line; carried out by sighting between a near and a far peg previously set in the gradient desired.
T-shaped rods used, in sets of three, to facilitate the process of Boning-in, two of the rods are held on the near and far pegs to establish a line of sight between them in the desired gradient, while the third is used to fix intermediate pegs in line.
A term used to describe a condition experienced when running out of energy while riding a bicycle or running.
  1. British term for vehicle hood to cover the front engine bay.
  2. A wire-netting cowl covering the top of a ventilating pipe or chimney.
  3. A movable protecting cover or cap of the valve-box of a pump.
  4. The cover plate of a valve chamber.
  5. The hood of forge.
Bonnet badge
British term for Hood badge
Bonnet bump rubber
British term for Hood bump rubber
Bonnet bumper
British term for hood bumper or Hood bump rubber
Bonnet landing panel
British term for Hood landing panel
Bonnet liner
British term for Hood liner
Bonnet lock
British term for Hood lock
Bonnet pin
British term for Hood pin
Bonnet pin kit
British term for Hood pin kit
Bonnet release
British term for Hood release
Bonnet stay
British term for Hood rod
Bonnet support
British term for Hood rod
Bonnet tape
British term for Hood tape
BOO Abbreviation for Brake On / Off Switch — which warns the PCM that brakes are applied
Booby Hatch
A watertight covering over a deck opening used for a stairway or ladder
Trucker slang for top gear as in ‘I’ve got ‘er up in the boogie now’
  1. Enhanced reverberation or resonance in an enclosed space at low frequencies.
  2. A long beam such as the top and bottom members of a built up girder.
  3. The main jib of a crane.
  4. A lifting mechanism. May be mounted on or as part of the cargo body of a truck. Booms are common on utility trucks or flatbeds.
  5. A spar holding the lower part of a fore-and-aft sail.
  6. A spar attached to a yard to lengthen it
  7. A barrier of logs to prevent the passage of a vessel.
  8. A line of floating timbers used to form a floating harbor.
  9. A pole marking a channel.
  10. A length of flexible tubing to contain an oil spillage.
  11. A long movable arm to carry a microphone or lamp above the action in film or television shooting.
  1. A noise caused by interruptions to the flow of air such as an open windows.
  2. Low pitched resonance, especially in the exhaust.
  3. Thumping sound coming from large stereo woofers.
Boom Rest
A support for a boom when the boom is not in use.
Boom Step
A socket for the end of a boom
  1. The amount of positive pressure created in an Intake system above normal atmospheric pressure by a turbocharger or supercharger. Normal atmospheric pressure is 14.7 psi. A Blower providing 10 psi boost increases the pressure to 24.7 psi. Boost is sometimes measured in atmospheres where one atmosphere equals 14.7 psi. Thus 24.7 psi is about 1.7 atmospheres.
  2. The action of Jump starting one battery from another.
  3. To increase power, charge, or pressure, etc.; or to amplify volume, audio sound, etc.
Boost-activated ignition retard
On a turbocharged engine, a system which retards the ignition timing when the intake manifold is under pressure, in order to reduce the chance of detonation.
Boost control
A device regulating reciprocating-engine manifold pressure so that supercharged engines are not over-stressed at low altitude.
Boost-controlled deceleration device
(BCDD) A valve that, during deceleration, is triggered into action by high intake manifold vacuum the BCDD valve allows an additional source of air and fuel to enter the intake manifold during deceleration to obtain a more burnable mixture.
Boost control cut-out
Boost control override
In a supercharged piston aero-engine fitted with Boost control, a device (sometimes lightly wire-locked so that its emergency use can be detected), which allows the normal maximum manifold pressure to be exceeded. Also called boost control cut-out
Boost control valve
  1. A radio device which amplifies the signal or the audio output to the speakers. Because of its size it is mounted in the glovebox, under the instrument panel, in the center console, under the seat, or in the trunk.
  2. A device incorporated in vehicle system (such as brakes and steering), to increase the pressure output or decrease amount of effort required to operate, or both.
  3. A common term applied to the case of a compressor when used as the first stage in the cascade refrigerating system.
  4. A rocket engine, or cluster of engines, forming part of a launch system, either the first stage or auxiliary stage, used to provide an initial thrust greater than the total lift-off weight. Also called booster rocket.
Booster amplifier
Amplifier used especially to compensate loss in mixers and volume-controls, so as to obviate reduction in signal-to-noise ratio.
Booster battery
A second battery used in commercial vehicles to give a little more power when starting.
Booster cables
Booster cables
Booster cable
Booster coil
A secondary ignition coil which increases the intensity of the spark.
Booster Dolly
A dolly usually at the rear of a truck or LCV and uses hydraulics to shift some of the load weight onto the rear dolly axles
Booster fan
A fan for increasing the pressure of air or gas; used for restoring the pressure drop in transmission pipes, and for supplying air to furnaces
Booster holding position
The point at which a booster maintains a constant level of power assist
Booster pump
A pump which maintains positive pressure between the fuel tank and the engine, thus intensifying the flow. Any pump to increase the pressure of the liquid in some part of a pipe circuit.
Booster rocket


Booster seat
A recommended seat for children who have outgrown a child safety seats. Children who fit that description should be properly restrained in booster seats in the back seat until they are at least 8 years old or more than 145cm tall. A booster seat positions a child so a safety belt can fit correctly. Without a booster seat, a small child can be ejected from a vehicle in a crash.
Booster station
Station which rebroadcasts a received transmission directly on the same wavelength
Booster transformer
A transformer connected in series with a circuit to raise or lower the voltage of the circuit.
Booster vacuum runout point
The point at which a Vacuum booster is supplying the maximum amount of power assist possible. Any additional braking force must be applied at the brake pedal.
Booster venturi
A small venturi located immediately above and concentric with the main venturi in a carburetor. Boosters are designed to amplify the weak venturi vacuum signal that occurs during low airflow conditions.
Boost gauge
  1. An instrument or meter which indicates Boost pressure
  2. An instrument for measuring the manifold pressure of a supercharged aero-engine in relation to ambient atmosphere or in absolute terms. Also used for racing and other car sports.
Boost pressure
Pressure in the intake system of a supercharged engine when the supercharger operates. See the first definition of Boost.
Boost regulator
Voltage conversion device used to raise the voltage in a DC system.
Boost sensor
A sensing device in a supercharger. It is located in the choke tube which sends a signal to the ignition control unit according to pressure conditions. In turn, the control unit adjusts the ignition timing for the best performance.
Boost transformer
Boost valve
A valve in a hydraulic system which increases the pressure.
  1. British term for a trunk.
  2. The rubber or plastic cover located at either end of the spark plug cable to insulate the connections between the cable ends and the spark plug and distributor terminal. Always grasp the cable by the boot when removing it.
  3. A flexible rubber or plastic cover used over the open ends of the Master cylinder and wheel cylinder to keep out water and other foreign matter
  4. The protective cover of the Ball joint that holds the Grease.
  5. The cover that protects the suspension forks on a bicycle or motorcycle from dirt and grime.


  6. A protective cover surrounding the Constant velocity joint
  7. A simple protective device (sometimes a piece of tube, tire, etc., cut to size) placed between the casing and tube. It offers temporary protection for the tube against pinching by an injury in the casing. It is not a repair of the injury and is unsafe to use.
  8. A covering over the lowered convertible top. It may be flexible (canvas or vinyl) or rigid (fiberglass or metal). Also called a top boot
  9. A Denver boot, which is a device which clamps on the wheels of a parked car to immobilize it. Also called a Heavy yellow boot.
  10. A colloquial term for the action of going very fast as in, We were booting along as fast as the snowmobile would go.
  11. To accelerate rapidly as in, When the light turns green, boot it.
A vehicle which has been disabled by a Denver boot is said to be booted.
Booted version
British term for Trunk model
Boot handle
British term for Trunk handle
British term for Trunk lid
Boot puller


Boot spoiler
British term for Trunk spoiler
A self-sustaining system in liquid rocket engines by which the main propellants are transferred by a turbo-pump which is driven by hot gases. In turn the gas generator is fed by propellants from the pump.
Bootstrap circuit
A feedback circuit in which part of the output is fed back across the input giving effectively infinite input impedance and unity gain. Often used to improve the linearity of a voltage sweep generator.
The technique of using bootstrap feedback.

Boot tapping
The demarcation line between the two main colors of a ship’s paintwork, at or near the water line.
Boral sheet
A composite made of boron carbide crystals dispersed in aluminum and also faced with aluminum. Used as a neutron absorber.
A pile driven to support the sides of a coffer-dam
Border shopping
  1. The area of a cylinder hole through which a piston travels back and forth
  2. The diameter or width of the cylinder.
  3. The internal walls of the cylinder.
  4. The circular hole along the axis of a pipe or machine part.
  5. As a verb, it means to cut a circular hole.
  6. With the word full it means to go fast.
To increase the diameter of the cylinder.


Bore diameter
The diameter of the cylinders. It is usually measured in either inches or millimetres. When a cylinder is bored out because of scored walls, it is increased by ten thou of an inch (0.01′) or 0.25 mm.
Bore-stroke ratio
The relation between the diameter of the cylinder bore and the length of the stroke of the piston. If the stroke is longer than the cylinder bore diameter then the engine is called a Long stroke engine. If the stroke is shorter than the cylinder bore diameter then the engine is called a Short stroke engine. If the stroke is the same as the distance of the cylinder bore diameter then the engine is called a Square engine
BorgwardClick image for books on

A German automobile manufacturer which began by Carl F. W. Borgward in 1921.

  1. The process of machining a cylindrical hole, performed in a lathe, boring machine, or boring mill; for large holes, or when great accuracy is required, it is preferable to using a drill.
  2. Renewing the cylinders by cutting them out to a specified size, a Boring bar is used to make the cut.
Boring bar
  1. A machine with a stiff bar that has multiple cutting bits used to cut engine cylinders to a specific size. As used in garages, to cut worn cylinders to a new diameter or bearing bores in proper alignment with each other.
  2. A bar clamped to the saddle of a lathe or driven by the spindle of a Boring machine, and carrying the Boring tool.
Boring machine
A machine on which boring operations are performed, comprising a head, carrying a driving-spindle, and a table to support the work.
Boring mill
A vertical boring machine in which the boring bar is fixed, the work being carried by the rotating table.
Boring tool
The cutting tool used in boring operations. It is held in a Boring bar
Born-Oppenheimer approximation
An approximation used in considering the electronic behavior of molecules. The problems of the electronic and nuclear motion are treated separately.
Boron chamber
Counter tube containing boron fluoride, or boron-covered electrodes, for the detection and counting of low-velocity neutrons, which eject α-particles from the isotope boron-10. Also called boron counter.
Boron counter
Borrow pit
Excavation which provides material to serve as fill when required.
Boron fiber coated with silicon carbide
The tapering portion of a Blast furnace, between the largest diameter (at the bottom of the stack) and the smaller diameter (at the top of the hearth).


  1. An extension or strengthened section or projection (usually cylindrical) that holds the end of a pin or shaft. For example, the holes in the piston through which the Piston pin is placed would easily break the thin walls of the piston when under pressure. The area around the hole (on the inner side of the piston) are strengthened to prevent breakage. This area is the Piston boss.
  2. The curved swelling portion of the ship’s hull around the propeller shaft.
The raised ledges or platforms on a backing plate that support the brake shoes
Boss Frame
A hull frame which is bent for clearing propeller shaft tube boss
Bossing mallet
A hammer with a pear-shaped wooden head used for shaping and stretching metal over a sandbag or wooden block.
Boss Plate
A shell shaped plate covering the curved portion of the hull where the propeller shaft passes outboard.
  1. A repair job which is very poorly done.
  2. To do a repair job poorly.
Botched-up job
A colloquial term for a poor repair which will not be permanent.
A cargo tank of a truck or trailer designed to carry liquefied or compressed gases. Examples include bottled gas, propane, and butane.

Bottle cage

Bottle cageBottle cage

A water bottle holding bracket which is mounted to the frame of bike either with a clamp or by screws into a pair of braze-on nuts

Bottled gas
(LPG) Liquefied petroleum gas or Propane) gas compressed into strong metal portable tanks. The gas, when confined in the tank, under pressure, is in liquid form.
Bottle jack

Bottle jackBottle jack

A hydraulic lifting device which is in the shape of a bottle

  1. A traffic situation where the road narrows to the point where traffic is excessively slowed.
  2. Product congestion in a warehouse where it is difficult to obtain the proper shipment at the right time
  1. The lowest point.
  2. To lower something.
  3. To reach the end of its travel (i.e., bottom out).
  4. To make contact with the road.
Bottom bracket

Bottom bracketBottom bracket

Bicycle component that is inserted into the bottom bracket shell. The bottom bracket consists of the crank axle (bottom bracket spindle), ball bearings, and (in older style bottom brackets) a fixed cup and an Adjustable cup. Crankarms are bolted to the bottom bracket.

Bottom bracket shell
The barrel shaped portion of the frame into which the bottom bracket is inserted. The seat tube, down tube, and chain stays are connected to the bottom bracket shell.
Bottom bracket spindle
The axle to which both of the crankarms are attached. The spindle length is measured in millimetres from one end of the spindle to the other.
Bottom dead center
(BDC) The lowest point of the piston and Connecting rod travel in a cylinder. In a horizontally opposed engine, it is sometimes called the Outer dead center. Opposite to Top dead center.

Bottom deck
Assembly of deck boards comprising the lower, load bearing surface of the pallet.
Bottom Diameter
The diameter of a circle measured between one toothgap and the opposite gap for a sprocket with even number of teeth.
Bottom Dump
Dry bulk truck bodies which empty their load by means of gravity alone through the bottom. Also called hopper-bottom or belly dump
Bottom dumps
Trailers that unload through bottom grates.
Bottom end
  1. All the moving parts in the crankcase and their bearings.
  2. The bottom part of the engine, where the crankshaft and usually the transmission resides
  3. The lower range of engine revolutions.
Bottom end gasket kit
All the gaskets below the base gasket (crankcase gaskets and inspection cover gaskets) and all the O-rings and replaceable spacers in the bottom end of an engine.

Bottom Freight
Heavy freight that must be loaded on the trailer floor and not on top of other merchandise.
Bottom gear
The lowest gear in a transmission.
  1. A situation where the suspension reaches the end of its travel.
  2. A situation where the lowest part of the chassis touches the ground, especially on a bump.
  3. The lowest layer of foundation material for a road or other engineering works including structures.
Bottoming cycle
A waste-heat recovery boiler recaptures the unused energy and uses it to produce steam to drive a steam turbine generator to produce electricity.
Bottoming tap
Tapping threads in a blind hole


Bottom out
To reach the end of its travel.
  1. A term used in connection with the Orford process for nickel and copper which have separated as sulfides. When the mixed sulfides are fused with sodium sulfide, the nickel sulfide separates to the bottom. Hence bottoms as distinct from tops.
  2. In reverberatory furnace, the heavier molten material at the bottom of pool.
Bottom tank
In a thermosyphon water-cooling system, this is the bottom radiator tank.

Boucherot circuit
An arrangement of inductances and capacitances, whereby a constant-circuit supply is obtained from a constant-voltage circuit.
A hollow plug or bushing inserted in watch or clock plates to form the pivot holes.
Bouguer law of absorption
Law stating that the intensity p of a parallel beam of monochromatic radiation entering an absorbing medium is decreased at a constant rate by each infinitesimally thin layer db, i.e., -dp/p = kdb where k is a constant that depends on the nature of the medium and on the wavelength
Trucker slang for interstate highway as in ‘Once we hit the boulevard we can put some miles behind us.’
  1. When referring to valves, it indicates a condition where the valve is not held tightly closed in the seat even though the camshaft has not opened it. Also called Flutter or Valve bounce
  2. When referring to a distributor, it indicates a condition where the points make erratic contact when they should remain closed.
  3. When referring to suspension, it indicates an up-and-down motion called Jounce and rebound. You can test it by pushing down and releasing a corner of a vehicle.
  4. The action of a vehicle dealer who increases the sale price of the vehicle, interest rate, monthly payments, etc.
Bouncing-pin detonation meter
An apparatus for determining quantitatively the degree of detonation occurring in the cylinder of a gasoline engine; used for fuel testing.
Boundary film
A film of one constituent of an alloy surrounding the crystals of another.
Boundary layer
The thin layer of fluid (air) adjacent to the surface in which viscous forces exert a noticeable influence on the motion of the fluid and in which the transition between still air and the body’s velocity occurs.
Boundary layer control
Modification of the airflow in the Boundary layer to increase lift and/or decrease drag by various means:

  • removal of the boundary layer by sucking through slots or porous surfaces
  • use of vortex generators to re-energize sluggish surface flow
  • ejection of high-speed air through slits
  • blowing, by propulsion efflux, over wing surfaces
Boundary layer noise
The noise occurring at high speeds due to the oscillations in the turbulent boundary layer at many frequencies and heard in cockpit and cabin.
Boundary lights
Lights defining the boundary of the landing area.
Boundary lubrication
A state of partial lubrication which may exist between two surfaces in the absence of a fluid oil film, due to the existence of adsorbed mono-molecular layers of lubricant on the surfaces.
Bound charge
The induced static charge which is bound by the presence of the charge of opposite polarity which induces it. Also, in a dielectric, the charge arising from polarization. Also called surface charge.
Bound electron
Bound electrons
Electrons in the inner orbits around the nucleus of the atom, they are difficult to move out of orbit.
Bound state
Quantum mechanical state of a system in which the energy is discrete and the wavefunction is localized, e.g., that of an electron in an atom, where transitions between the bound states give rise to atomic spectral lines.
Bourdon gauge
Bourdon tube
A circular, hollow piece of thin metal tubing that is used in some instruments, pressure on the hollow section causes it to attempt to straighten, the free end then moves a Needle on the gauge face. Used in pressure gauges.
  1. A sliding type of current collector, used on electric vehicles to collect the current from an overhead contact-wire. It consists of a bow-shaped contact strip, mounted on a hinged framework.
  2. A flexible strip of whalebone or cane, the ends of which are drawn together to give tension to a thread or line which is given a single turn around a pulley of a pair of turns, drill, or mandrel. It is used as a sensitive drive for these tools and was used traditionally for the making of accurate holes, esp. for clock pivots.
  3. The forward ‘pointed’ end of a vessel.
Bow compasses
Bowden cable
A wire control cable within a metal or rubber sheath and used for activating a valve, clutch, choke, or accelerator.
Bowden gauge
Form of pressure-sensitive Transducer
Bowden-Thomson protective system
A form of protective system for feeders, in which special cables, with the cores surrounded by metallic sheaths, are employed; a fault causes current to flow in the sheath and operate a relay to trip the circuit.
Bowditch’s rule
A rule for the adjustment of closed compass traverses, in which it may reasonably be assumed that angles and sides are equally liable to error in measurement. According to this rule, the correction in latitude (or departure) of any line = (Length of that line divided by Perimeter of traverse) times Total error in latitude (or departure)
A bent shape in an arc.
Bowl vent
(BV) Connects the float bowl to the carburetor’s air inlet. Depressurizes the fuel being pumped into the float bowl by the fuel pump and acts as a vapor separator by allowing vapors in the float bowl to escape into the carburetor air inlet. Bowl vents are cut at a 45-deg angle and face incoming air so that reference pressure remains the same regardless of airflow.

Bowl vent port
(BVP) The port in the carburetor which vents fumes and excess pressure from the float bowl to maintain atmospheric pressure.
Bow nut


Bow propeller
A ship’s propeller whose thrust can be directed at right angles to the ship’s axis, used in docking and maneuvering in a confined space. Angular thrust can also be provided to the stern.
A tanker used for refueling military ground vehicles or airplanes.
A spar projecting forward from the bow of a vessel used to attach sails and stays.
Bowstring bridge
An arched bridge in which the horizontal thrust on the arch is taken by a horizontal tie joining the two ends of the arch.
Bowstring suspension
A form of suspension for the overhead contact-wire of an electric-tramway system, in which the contact-wire is suspended from a short cross-wire attached to the bracket-arm of the pole.
Bow thrusters
A propeller at the bow of the ship, used during maneuvering to provide transverse thrust.
Bow wave
The wave disturbance emanating from the leading edge of an object moving through fluid, esp. the V-shaped surface wave associated with boats moving through water.
Bow wow
A vehicle in very bad shape. A dog.
A vehicle in very bad shape. A dog.
  1. A description of a vehicle shape in which each section is a box. For instance in a sedan, the engine section is the front box, the passenger compartment is the middle box, and the trunk is the third box–thus a sedan is a three-box configuration. A station wagon or SUV is a two-box. A minivan is a one-box.
  2. Colloquial term for a vehicle transmission.
  3. A term for an electrical or electronic device.
  4. A silencer.
  5. A colloquial term for a trailer or container for ocean carriers.
  6. The enclosed cargo space of a truck or trailer.
Box annealing
Heating to soften work-hardened material by placing the work in a sealed box inside the furnace in order to exclude air. Also called close annealing.
Box baffle
Box, with or without apertures and damping, one side fitted with an open diaphragm loudspeaker unit, generally coil-driven.
Box chronometer
The marine chronometer. The chronometer is normally supported on gimbals, inside a wooden box with a hinged lid.
Box culvert
A culvert having a rectangular opening.
Boxed rod
A Connecting rod in which the I-beam section has been stiffened by welding plates on each side of the rod.
A two-cylinder engine with the pistons opposing each other, resembling fists flying away from each other.
Boxer engine
A Horizontally opposed engine.
Box-frame motor
A traction motor in which the frame is cast in one piece instead of being split
Box member
A structural part made as a Box section
Box nut


Box-Out Repairs
Cracked areas of the pavement are milled out and filled with asphalt concrete. This type of repair may be performed on up to 20% of the pavement surface. A ‘train’ approach is used with a machine to mill out the broken areas, a grader and skid steer to remove the old material, a paving machine to place the new material, a roller for compaction, etc. Several days may be spent to perform this treatment on a mile of roadway. The work is often followed by the application of a surface treatment.
Box section
A closed panel structure of square cross section which is used to strengthen a vehicle’s underbody.
Box Section Construction
A construction formed of two U-channels joined together to create a long box. It is used in frames where greater strength is required than is provided by a U-channel.
Box spanner
A British term for a hollow tube with a socket at each end and two holes through which a bar can be inserted to turn the wrench. The bar is called a T-bar; but the British call it a Tommy bar
Box tool
A single-point cutting tool, set radially or tangentially, used in automatic screw machines and in capstan and turret lathes.
Box-type brush-holder


Box van
A British term for a Cube van with a large cargo box behind the driver’s cab.
Box wrench
A tool designed to secure or remove a bolt or nut. Each end of the wrench fits around the bolt head or nut. British term for ring spanner. In contrast, see Open end wrench.
A derogatory description of a car that has square angles instead of smooth curved lines.


Boyle’s Law
Law of physics which states that the volume of a gas varies as pressure varies, if temperature remains the same. Example, if absolute pressure is doubled on the quantity of gas, the volume is reduced one half. If the volume becomes doubled, the gas has its pressure reduced by half.
Boyle temperature
Temperature at which the second viral coefficient of a gas changes sign. Close to this temperature, Boyle’s law provides a good approximation to the equation of the state of the gas.
Boy racer
A low-cost car without much sophistication or performance; but it does have a very sleek and sporty appearance.
Boy’s camera
A camera for photographing lightning flashes, gyrating lenses separating the strokes.
Boy scouts
Trucker slang for State police as in ‘There’s a bunch of boyscouts waiting for you at the 157.’
  1. Abbreviation for Barometric pressure
  2. Abbreviation for Barometric absolute pressure sensor
  3. Abbreviation for Barometric pressure sensor
  4. Abbreviation for Between perpendiculars
  5. Abbreviation for Boiling point
  1. Abbreviation for bypass air valve
  2. Abbreviation for Bypass air solenoid
  3. Abbreviation for British Parachute Association
  4. Abbreviation for Mechanical Bypass Air
Abbreviation for bypass control solenoid valve


The center body pillar on sedans. It connect the sills and provides roof support. Sometimes referred to as simply post, as in 1957 Chevy two-door post. On a true Hardtop design these pillars are missing, leaving uninterrupted glass area along the sides of the car. Also called B-post.

B pillar


B post




The center body post on sedans. It connect the sills and provides roof support. Sometimes referred to as simply post, as in 1957 Chevy two-door post. On a true Hardtop design these pillars are missing, leaving uninterrupted glass area along the sides of the car. Also called B-pillar.

Abbreviation for Brake Pedal Position Switch
  1. Abbreviation for Exhaust back pressure valve
  2. Abbreviation for Back Pressure Sensor
Abbreviation for Back-Pressure Transducer
  1. Abbreviation for Bypass valve
  2. Abbreviation for Exhaust back pressure transducer valve
Abbreviation for Brake Pulse Width


Symbol for the SI unit of radioactivity.

Abbreviation for Business Route — a road through the main part of a municipality.


A protective cover, usually of leather or vinyl, which is mounted to the front of a vehicle to protect the finish from stones.

  1. A support beam to give reinforcement between two objects.
  2. A member connecting two nodes of a structure out of plane with the main members, for stiffening purposes. Depending on the applied loads it may be subject to tensile or compressive forces. Also called swaybrace.
  1. To stiffen something by using a Brace.
  2. The staying or supporting rods or ties which are used in the construction or strengthening of a structure.
  3. A Brace.
  4. Wood or metal supports used to secure freight in place when loaded on a trailer.
Bracing wires
The wires used to support the wings of biplanes and the earlier monoplanes.
A support device which is often a right-angled shape or triangle shape designed to support or mount something

Bracket arms
The transverse projecting arms on the poles, for supporting the overhead contact wire equipment for a tramway or railway system.
Bracket set
Bracket shell
Bracket spindle
Bracket Splined
Bracket Square Tapered
Braided hose
A rubber hose which is covered in a woven material or braided wire. Used for various hoses under the hood.
  1. To slow down a vehicle.
  2. The mechanism that converts motion (Kinetic energy) into heat energy through friction. The most common instance is found in the wheels of cars where the brake shoes or disc pads are designed to press against the Brake drum or Brake disc.


Brake actuator
A unit which converts hydraulic pressure, air pressure, vacuum, or electrical current or other forms of energy to a force which applies a brake.

Brake actuator cam
A small cam that pivots in the brake backing plate and forces the brake shoes into the brake drum.
Brake adjuster
  1. A device which moves the brake drum shoes closer to or further apart from the drum.
  2. A device or mechanism used to set and maintain the proper clearance between the brake lining and drum.
Brake adjusting spanner
A British term for Brake wrench
Brake adjusting wrench
A tool used to adjust the brake shoes.
Brake anchor
A steel Stud or pin upon which one end of the brake shoes is either attached to or rests against. The anchor is firmly affixed to the backing plate.
Brake, anti-lock
Brake antiroll device
Brake anti-roll device
A unit installed in the brake system to hold Brake line pressure when the vehicle is stopped on an upgrade, when the vehicle is stopped on the upgrade and the brake pedal released, the anti-roll device will keep the brakes applied until either the clutch is released or as on some models, the accelerator is depressed.
Brake Application
Brake assembly
An assembly of the non-rotational components of a brake including its mechanism for development of friction forces.
Brake backing plate

Brake backing plateBrake backing plate

A rigid metal (steel) plate, located inside the Brake drum, on which the wheel cylinder, brake shoes, and other brake parts are mounted. The braking force applied to the shoes is absorbed by the backing plate.

Brake balance
  1. The ratio of front-to-rear braking force.
  2. The split of braking power between the front and rear axles. Proper brake balance allows the driver to use the full braking ability at all four wheels when stopping the car.
Brake band
  1. A band, faced with Brake lining, that encircles a Brake drum, it is used on several Parking brake installations. It differs from brake shoes in that brake shoes squeezes against the inside surface of a drum while a brake band squeezes against the outside surface of a drum.
  2. A flexible circular metal band which surrounds a brake drum and contracts around it to create the friction necessary to stop the vehicle. The rubbing surface of a brake band is faced with a brake lining material.
Brake bias
The front/rear distribution of a vehicle’s braking power. For the shortest stopping distance, Brake bias should match the vehicle’s traction at each end during hard braking brake modulation — the process of varying pedal pressure to hold a vehicle’s brakes on the verge of Lockup. Ideally, the brakes will unlock with only a slight reduction in the pressure needed to lock them. Typically, however, a considerable pressure reduction is required.
Brake bleeder
A valve attached to each wheel brake. This valve can be opened and closed to allow air to be removed or bled from the Brake lines.
Brake bleeding
Brake block
A molded piece of friction material attached to shoes and pads to serve as the brake lining.


Brake booster

Brake boosterBrake booster

  1. A mechanical device which attaches to the brake system to multiply the force the driver applies with his foot (or hand as in the case of a motorcycle). The device uses air, vacuum, or hydraulic fluid to accomplish this purpose. Sometimes called power assisted brakes, vacuum assisted brakes, hydraulically assisted brakes, or just Power brakes. In most cars, the Boost comes from engine Intake vacuum. In motorcycles it comes from hydraulic fluid.
  2. A device using a supplementary power source to reduce pedal (or lever) force in a hydraulic brake system.
  3. An arch (usually built from aluminum or carbon fiber) which attaches to the brake bosses of a bicycle in conjunction with the brake. The powerful braking force of V-Brakes or linear pull brakes can cause frames and forks to flex and waste energy which could have been applied to the rims. The booster acts as a brace to prevent frame flex induced during braking.
Brake boss
The brazed-on pivots attached to frames and forks for cantilever and V style brakes. Shift lever bosses are brazed-on pivots for down-tube-mounted shift levers. Most newer ‘road’ bicycles have the shifters mounted on the handlebars, so they use the old-style lever bosses as attachment points for housing stops.
Brake cable
  1. A wire cable which activates the brakes. Used on motorcycles, trailers, and automobile parkbrakes.
  2. A wound steel cable running from the brake levers of a bicycle to the brake calipers.
Brake cable housing
The outer, colored housing into which a brake cable is inserted.
Brake caliper
  1. The component of a disc brake that converts hydraulic pressure into mechanical energy.
  2. The device in a disc brake that converts hydraulic pressure back into the mechanical force used to apply the brake pads against the rotor.


Brake chamber
A unit in which a diaphragm converts pressure to mechanical force for actuating a brake.
Brake check
Trucker slang for jamming on your brakes in traffic as in ‘Watch out we’re doing a break check up ahead.’
Brake check valve
Brake console
Brake Control
Brake controller
Brake cylinder
  1. A cylinder containing a movable piston actuated by hydraulic pressure to push fluid through the lines and wheel cylinders and force the brake lining or pads against a drum or disc.
  2. A unit in which a piston converts pressure to mechanical force for actuation of a brake.
Brake disc
  1. The component of a disc brake that rotates with the wheel and is squeezed by the brake caliper and pads, which creates friction and converts the energy of the moving vehicle into heat.
  2. The parallel-faced, circular, rotational member of a brake acted upon by the friction material.
  3. A British term for Brake rotor.
Brake disc type
A braking system that instead of using the conventional Brake drum with internal brake shoes, uses a steel disc with caliper type lining application, when the brakes are applied, a section of lining on each side of the spinning disc is forced against the disc thus imparting a braking force. This type of brake is very resistant to Brake fade.

Brake Distribution
Brake dive
The action of the front end of a vehicle as it dips down when the brakes are applied. Opposite to Squat.

Brake drag
Failure of the brakes to release completely when the driver’s foot is removed from the pedal.
Brake drum

Brake drumBrake drum

  1. A Cast iron or Aluminum Housing bolted to the wheel, that rotates around the brake shoes. When the shoes are expanded, they rub against the machined inner surface of the brake drum and exert a braking effect upon the wheel to slow or stop the vehicle. In some cases an external band surrounds the drum to reduce the motion of the wheel.
  2. The rotating cylindrical component of a drum brake system on which the brake shoes act to slow or stop the vehicle.
Brake drum lathe
A machine to refinish the inside of a Brake drum.
Brake dust
The fine particles created as the brake linings wear down in normal use. Brake dust usually contains dangerous amounts of asbestos
Brake dynamometer
A device that measures the power and torque of an engine by restricting its speed (braking) so as to gauge its output
Brake effectiveness buildup
A temporary increase in brake effectiveness during a stop or Snub.
Brake efficiency
The retarding force expressed as a percentage of the total vehicle weight
Brake extension
Brake fade
  1. Reduction or loss in braking force due to loss of friction between brake shoes and Drum (or Brake pads and disc). Caused by heat buildup through repeated or prolonged brake application.
  2. The partial or total loss of braking power that occurs when excessive heat reduces friction between the brake linings and the rotor or drum.
Brake failure
The total inability of the brakes to function. May be caused by worn out pads or shoes, broken hydraulic lines, broken cable or other linkage, non-functioning master cylinder, low or empty brake fluid reservoir, etc.
Brake feel
A discernible, to the driver, relationship between the amount of brake pedal pressure and the actual braking force being exerted. A special device is incorporated in Power brake installations to give the driver this feel.
Brake fluid
A special fluid used in Hydraulic brake systems to stop or slow the vehicle. Never use something else in place of regular fluid. Brake fluid must be resistant to heating, freezing, and thickening. There are four types of brake fluid on the market.

Brake fluid level indicator
A unit in a hydraulic brake system which indicates the amount of brake fluid.
Brake fluid level warning switch assembly
A unit used to actuate a warning device indicating a reservoir fluid level lower than a preset value.
Brake fluid reservoir
In an automobile, it is a translucent tank located in front of the master cylinder. It usually has two chambers containing brake fluid. In a motorcycle, it may be found on the handlebar (for the front brake) or near the back of the bike (for the rear brake).
Brake fluid warning light
Indicator light located in the instrument cluster used to indicate a problem in the brake hydraulic system.
Brake flushing
Cleaning the brake system by flushing with alcohol or brake fluid. This is done to remove water, dirt, old brake fluid, or any other contaminant. Flushing fluid is placed in the master cylinder and forced through the lines and wheel cylinders where it exits at the cylinder Bleed screws.
Brake gauge
Brake handle
A hand-operated lever which, when actuated, causes the brake(s) to be applied.
Brake hood

Brake hoodBrake hood

A plastic, rubber, or leather covering mounted around the brake levers to keep out the dust and to provide a non-abrasive placement for the hands during cycling

Brake horsepower
(bhp) A measurement of the actual usable power (not calculated power) measured at the output shaft (usually the crankshaft) rather than at the driveshaft or the wheels. Thus none of the auxiliaries (gearbox, generator, alternator, differential, water pump, etc.) are attached. It is called the brake horsepower because the shaft power is usually measured by an absorption dynamometer or brake. This is not the brake on the vehicle’s wheels but a testing device applied to the shaft. This instrument is applied to stop or absorb the rotation of the output shaft and returns a value. One bhp = 746W or (approx) 3 bhp = 4kW.

Brake hose
A flexible high-pressure hose that is reinforced. It connects between the brake pipes and the brake assembly. It needs to be flexible because of the constant movement of the suspension.
Brake hose coupler
A separable mechanical connector for a brake hose between the towing and the towed vehicle.
Brake judder
A condition where the brake pads make intermittent contact because of a worn rotor. It sounds and feels like rapid vibration. It is also the normal condition in an ABS brake system when the brake is applied (often to the surprise of the driver) as the ABS system rapidly engages and disengages the pressure of the brake pads on the rotor.
Brake lathe
  1. The machine used to resurface the friction surfaces of brake discs or drums.
  2. A machine used to refinish brake drums and disc brake rotors.
Brake lever

Brake leverBrake lever

  1. A blade attached to the right side of a motorcycle handlebar which usually activates the front brake.
  2. A device for activating the park brake.
  3. A curved blade found on either side of a bicycle handlebar which activates the front or rear brakes.
Brake Lever Combo
Brake lever strut
Brake light
A red light at the rear of the vehicle which is activated when the brakes are applied. Also called stop light.

Brake light switch
An electrical switch, operated either mechanically or hydraulically (depending on the car) causes the brake lights to come on when the brakes are activated.
Brake line
Brake lines
  1. A system of hoses and metal tubes through which the brake fluid flows from the master cylinder to the brake calipers at each wheel. Cracks or breaks in these lines will cause the fluid to leak out and result in loss of brakes.
  2. Small-diameter rigid steel tubing used to channel hydraulic pressure from the Master cylinder to the wheel cylinder or caliper in a brake system. May have either a double or ISO flaring at fittings.
Brake lining
  1. A heat-resistant friction material (usually asbestos) that is attached to the brake shoe (either riveted or bonded). When the shoe is pressed against the Brake drum, the lining grabs the inside of the drum, which stops the vehicle and also prevents the drum and the shoe from wearing each other away.
  2. A special friction material with which brake shoes or brake pads are lined. It withstands high temperatures and pressures. The molded material is either riveted or bonded to the brake shoe, with a suitable coefficient of friction for stopping a vehicle.
Brake lining wear sensor
A unit used to actuate a warning device indicating a brake lining thickness less than a preset value.
Brake lock
Brake magnet
A permanent magnet or electromagnet which produces a braking effect, either by inducing eddy currents in a moving conductor or by operating a mechanical brake by means of a solenoid.
Brake master cylinder
Brake master cylinderClick image to supersize
Brake master cylinder

The part of the Hydraulic brake system which stores the brake fluid. As the brake pedal is applied pressure is forced against a small movable piston in the master cylinder to push hydraulic fluid through the lines to the wheel cylinders and force the Brake linings against the Drum (in the case of drum brakes) or force the Brake pads against the disc (in the case of disc brakes).

Brake mean effective pressure

  1. The average pressure in the cylinders of an engine divided by its mechanical efficiency, i.e., the ratio of the power actually delivered at an output shaft to the power developed in the cylinders. It is used as an indication of torque.
  2. That part of the Indicated mean effective pressure (IMEP) developed in an engine cylinder output equal to the brake horsepower of the engine; the product of IMEP and mechanical efficiency.
  3. The work accomplished during one engine cycle divided by the engine swept volume. It is essentially the engine torque normalized by the engine displacement. The word brake denotes the actual torque/power available at the engine flywheel as measured on a dynamometer. Thus, BMEP is a measure of the useful power output of the engine.
Brake Metering Valve
Brake metering valveClick image to supersize
Brake metering valve

In order to insure that the back drum brakes apply at about the same time as the front discs and that the drum brakes do an equal amount of work during light stopping, a metering valve is placed in the line to the disc brakes. The metering valve prevents brake fluid movement to the discs until a specified number of psi has been built up in the system. By the time the system pressure reaches this point, the force of the heavy drum brake shoe retracting springs has been overcome, and the shoes are starting to contact the drum. The metering valve then opens and allows fluid pressure to apply the disc brakes. No residual pressure is maintained in the front disc system.

Brake pad

Brake padAutomotive Brake pad

  1. The friction material or lining which is secured to metal plates. They press against the Brake disc or rotor to enable the wheel to stop. They are to be distinguished from brake shoes which press against the inside of a Drum.
  2. Bicycle Brake PadBicycle Brake Pad

    On a bicycle, brake pads are blocks of rubber-like material fastened to the end of the brake caliper; they press against the wheel rim when the brakes are applied. Also called brake block. Sometimes the term brake pad refers to both the pad and the metal backing.

Brake pads


Brake pad wear indicator
A device which detects the thickness of the brake pad by using an L-shaped strap which will scrape against the disc when the pad thickness is below tolerance. Others use an electrical circuit in which a worn pad closes an electrical circuit that illuminates a light on the instrument panel.
Brake parachute
Parachute attached to the tail of some high-performance aircraft and streamed as a brake for landing. Sometimes a ribbon canopy is used for greater strength and on large aircraft a cluster of two or three is required to give sufficient area with convenient stowage. Also called landing parachute and parabrake.
Brake pedal
Brake pedalClick image to supersize
Brake pedal

A foot operated device which engages the brakes to stop or slow the rotation of the wheels.

Brake pipe
A steel pipe used to transmit the brake fluid.

Brake piston
On a motorcycle, pressure from the brake lever (when squeezed) forces the brake fluid to flow from the master cylinder down through the brake line and into the caliper. The pressure of the brake fluid causes the piston to push the brake pad to rub against the disc, thus stopping movement of the motorcycle.
Brake piston tool

Brake piston toolBrake piston tool

A disk brake tool used to rotate the piston back into the caliper when replacing pads

Brake, power
Brake power assist
A device installed in a hydraulic brake system that reduces pedal effort.

Brake pressure modulator valve
(BPMV) A combined assembly of the electronic control unit and hydraulic control unit, used in some General Motors vehicles. Also called the Electro-Hydraulic Control Unit (EHCU).
Brake Pressure Type Check Valve
Brake puck
Brake pucks
Brake pulling
A situation where the vehicle moves to one side when the brakes are applied. It is usually due to uneven application of the brakes from side to side.
Brake, parking
Brake proportioning valve

Brake proportioning valveBrake proportioning valve

A valve that limits braking force to the front or rear wheels, usually as a function of pedal effort or line pressure, loading of the vehicle or front-rear weight transfer, to prevent wheel locking and provide the most effective braking.

Brake retarder
An auxiliary energy conversion system used to supplement the Service brake unit on a moving vehicle.
Brake rod
A long rod which connects between the brake pedal and the brake actuating lever.
Brake rotor
The Brake disc which is attached to the wheel and is surrounded by a brake caliper.

Brakes, cantilever
Brake servo
A device which multiplies the driver’s physical effort in applying the brakes by using manifold vacuum.
Brake servo unit
Brake shoe
Brake shoeClick image to supersize
Brake Shoe
  1. That part of the brake system, located at the wheels, upon which the Brake lining is attached. There are usually two shoes (curved or arc-shaped pieces) in each wheel. When the wheel cylinders are actuated by hydraulic pressure they force the brake shoes apart and bring the lining into contact with the Brake drum. In this way the vehicle is slowed or stopped. On a bicycle, it is the metal part that holds a Brake pad and is bolted to the end of a brake caliper.
  2. A crescent-shaped (for drum brakes) or a square/rectangular (for disc brakes) piece of metal faced with brake lining material and forced against the revolving drum or disc to create friction. In a disc brake system, the brake shoe may be called a brake pad.
Brake shoe grinder
A grinder used to grind brake shoe lining so that it will be square to and Concentric with the Brake drum.
Brake shoe heel
That end of the brake shoe closest to the Anchor bolt or pin.
Brake shoe hold-downs
Spring-loaded retainers that hold brake shoes against the backing plate.
Brake shoe return spring
A spring which is attached to the two brake shoes. After the brake is applied, this spring pulls the shoes away from the drum.
Brake shoes
The components of a drum brake assembly that are surfaced with brake lining and forced against the brake drum to generate friction.
Brake shoe toe
The free end of the shoe, it is not attached to or resting against an Anchor pin.
Brake shudder
A condition where the brake pads make intermittent contact because of a worn rotor. It sounds and feels like rapid vibration. It is also the normal condition in an ABS brake system when the brake is applied (often to the surprise of the driver) as the ABS system rapidly engages and disengages the pressure of the brake pads on the rotor.
Brake snub
The act of retarding a motor vehicle between two positive speed values by the use of a brake system
Brake snubbing time
Time elapsed during a brake snub from the start of brake application to the instant the lower speed value is reached.
Brake Specific Fuel Consumption
(BSFC) The ratio of the engine fuel consumption to the engine power output (as measured at the flywheel). BSFC has units of grams of fuel per kilowatt-hour (g/kWh) or pounds mass of fuel per brake horsepower-hour (lb/bhp-hr). BSFC is a measure of engine efficiency.
Brakes, power
Brake stopping distance
Distance traveled by a motor vehicle from the start of a brake application to the point at which the motor vehicle reaches a complete stop.
Brake stopping time
Time elapsed by a motor vehicle from the start of a brake application to the instant the motor vehicle reaches a complete stop
Brake Supply Line
Brakes V


Brake system
A system that uses hydraulic pressure to enable your vehicle to slow and stop safely. Consists of the master cylinder, Brake lines, and disc or drum brakes at each wheel.

Brake system actuation distance
The distance traveled between the start of brake application and the instant at which a specified brake system pressure is obtained
Brake system actuation time
The time elapsed between the start of brake application and the instant at which a specified brake system pressure is obtained
Brake system cleaner
A type of solvent designed exclusively for cleaning brake system components. It will not destroy plastic, rubber, or synthetic rubber components and it dries quickly, without leaving a residue.
Brake test
A testing procedure which determines the efficiency of a vehicle’s brakes in order to pass safety tests.
Brake thermal efficiency
The efficiency of an engine reckoned in terms of the brake horsepower; given by the ratio of the heat equivalent of the brake output to the heat supplied to the engine in the fuel or steam.
Brake thermo efficiency
The ratio of the useful power output of an engine to the fuel energy per unit time.
Brake torquing
A procedure generally used in performance tests to improve the off-the-line acceleration of a vehicle equipped with an automatic transmission. It is executed by firmly depressing the brake with the left foot, applying the throttle with the vehicle in gear to increase engine rpm, then releasing the brakes. Brake torquing is particularly effective with turbocharged cars because it helps overcome Turbo lag.
Brake Valve
Brake warning light
An indicator light on the instrument panel which indicates problems such as low fluid level in the brake fluid reservoir, a malfunction in any of the hydraulic brake circuits, or excessive wear of the brake pads or shoes. It also illuminates when the parkbrake is applied. When the ignition is first started, the light will illuminate momentarily to show that the light is working.
Brake Warning Switch Assembly
Brake wear indicator
Index grooves, tabs, or reference lines to indicate the amount of brake pad or lining that is still remaining or has been used up.
Brake wrench
A wrench which is used to adjust the brake shoes. The British call it a brake adjusting spanner
The action of operating the devices for slowing the motion of a vehicle.

Braking distance
A measurement of the distance that a vehicle will travel from the time the brakes are first applied to the actual moment it stops.

Braking effect
Braking efficiency
Braking effort as a percentage of the weight of the vehicle.
Braking effort
The amount of strength needed by the operator to bring a vehicle to a stop or the amount of resistance in the brake system.
Braking force
The amount of strength needed by the operator to bring a vehicle to a stop or the amount of resistance in the brake system.

Braking force ratio
The sum of the retarding forces developed by each braked wheel divided by the as tested gross mass of the vehicle or combination.
Braking notches
Positions of the angle of a drum-type controller which apply some form of electric braking.
Braking ratio
The distribution of braking effort between the front and rear wheels.
Braking system
All the components that contribute to stopping the vehicle.

Braking time
Braking Torque
  1. The torque required to bring an electric motor down from running speed to a standstill.
  2. The torque developed by an electric motor during dynamic braking conditions
  1. An alternative mode of radioactive decay.
  2. Electric components comprising a minimum path between junction points of common connection in a network. Also called arm
A circuit branched off a main circuit.
The existence of two or more modes or branches by which a radionuclide an undergo radioactive decay, e.g., copper-64 can undergo β , β + and electron-capture decay
Branch jack


Branch switch
A term used in connection with electrical installation work to denote a switch of any type for controlling the current in a branch circuit.
Branded product
A refined petroleum product sold by a refiner with the understanding that the purchaser has the right to resell the product under a trademark, trade name, service mark, or other identifying symbol or names owned by such refiner.
Brand number
A series of identifying numbers and letters which some companies burn into the sidewall rubber of a truck tire to show their initials, mounting date, etc.
A Brazilian communications satellite system
An alloy of copper and zinc, but other elements such as aluminum, iron, manganese, nickel, tin, and/or lead are frequently added. There are numerous varieties. It is non-magnetic with good strength and toughness, high electrical conductivity, and an attractive lustrous finish. It has good corrosion resistance but not in salt water. Brass is commonly used by the electrical and communications industries, builders hardware, and some marine applications.

Brass Car
A vehicle built prior to 1915 sometimes called the brass era because of the widespread use of fancy brass fittings and brass lanterns that were a natural addition to the new ‘horseless carriage.’ The Brass era lasted from around 1905 to 1914. This was the beginning of mass produced affordable vehicles for the common public rather than the domain of the elite. Also called an Antique car
Those parts of a bearing which provide a renewable wearing surface; they consist of a sleeve or bored block of brass split diametrically, the two halves being clamped into the bearing block by a cap.
Brass hammer

Brass HammerBrass Hammer

A hammer with a brass head which is used to pound steel pins etc. into place without damaging them because the brass head is softer than steel.

Brass punch
A Drift or punch made of brass which is used to remove bushings and bearing races because brass does not score or mark steel.
Brass Thread
Braun tube
Original name for Cathode-ray tube, after K. F. Braun (1850-1918) the inventor.
Oldsmobile Bravada BooksClick image for books on
Oldsmobile Bravada

A model of an SUV automobile built by Oldsmobile from 1991-2004

Brayton cycle
A constant-pressure cycle of operations used in gas turbines.
To join two pieces of metal together by heating the edges to be joined and then melting drops of brass or bronze on the area. Unlike welding, this operation is similar to soldering, except a higher melting point material is used.
Braze on




Parts for mounting shift levers, cable guides, pump pegs, chain hangers, front and rear eyelets, derailleurs, water bottle Cages, and racks, which are fastened to a bicycle frame through a type of Soldering process known as brazing.

Braze welding
Making an adhesion groove, fillet, or plug connection with a brazing alloy.
Making an adhesion groove, fillet, or plug connection with a brazing alloy, brass, spelter, or Brazing solder between the adjoining surfaces.

Brazing solders
Alloys used for brazing. They include copper-zing (50-55% copper), copper-zinc-silver (16-52% copper, 4-38% zinc, and 10-80% silver), and nickel-silver alloys.
Brazing flux
Substance applied to surfaces to be joined by brazing or soldering to keep oxides from forming and to produce joints.


Breadth coefficient
Breadth factor
  1. The action of an item when it no longer holds integrity — usually resulting in unusable pieces.
  2. The shortest distance between the contacts of a switch, circuit breaker, or similar apparatus, when the contacts are in the fully open position.
  3. To dismantle a vehicle for parts.
  4. To separate as when a switch breaks contact when it is shut off
  5. Trucker slang for ‘I’d like to break-in’ or ‘interrupt’ as in ‘Can I get a break?’
Trucker slang for ‘I want to talk (on channel 10)’ as in ‘Can I get a break one-oh?’
Break away


The action of a wheel when it turns very rapidly and loses traction so that there is no contact with the ground. Bias-belted tires and radial tires resist the breakaway action better than a bias ply tire.

Breakaway barricade

Breakaway barricadeBreakaway barricade

A road obstruction which is designed to warn motorists that the road is unpassable or that there is construction in a particular lane. It is easily dismantled (thus breakable).

Break Bulk
  1. To unload, sort, and reload some or all contents of a vehicle in transit.
  2. To reduce a large shipment of a single commodity to many small shipments, which are then dispersed to various buyers.
Breakbulk vessel
A general, multipurpose, cargo ship that carriers cargoes of nonuniform sizes.
Break down
  1. To cease to operate as in our car broke down on the highway.
  2. To lose its insulating effectiveness. The sudden passage of current through an insulating material at Breakdown voltage.
  1. A failure of a mechanism or vehicle as in we had a breakdown on the highway.
  2. A loss of insulating effectiveness. The sudden passage of current through an insulating material at Breakdown voltage.
Breakdown crane
A portable jib crane carried on a railway tram or tow-truck, for rapid transit to the scene of an accident.
Breakdown diode
Breakdown recovery
Rescue of a vehicle that has suffered a breakdown by towing it to a service station, etc.
Breakdown service
A service provided by a tow-truck in providing repairs at the place where the breakdown occurred.
Breakdown Time
A type of penalty pay which is incurred when equipment breaks down.
Breakdown Torque
The maximum torque of an electric motor that will develop at rated voltage without a relatively abrupt drop or loss in speed
Breakdown truck
A tow-truck.
Breakdown voltage
(BDV) The potential difference at which a marked increase in the current through an insulator or a semiconductor occurs.
  1. A person who dismantles a vehicle for parts. Also called a dismantler.
  2. A cushioning layer between the belt layers and the tread in radial tires.
  3. A device for removing contact.
  4. A Circuit breaker
  5. The tread bracing part of tire.
  6. Trucker slang for a CB’er who asks to use a channel as in ‘Who’s that breaker out there?’
Breaker arm
The movable part of a pair of Contact points in a distributor or magneto.
Breaker cam

Breaker camBreaker cam

The lobed cam rotating in the ignition system which interrupts the Primary circuit to induce a high tension spark for Ignition.

Breaker gap
Breakerless transistorized ignition
A distributor or ignition system where the mechanical switching device (such as points or contacts) are replaced by an electronic switching device through the use of transistors. They are also called contactless or all-electronic ignitions.
Breaker plate
  1. The movable plate inside the distributor to which the points and the condenser are attached.
  2. Device fitted in front of the extruder screw to aid mixing.
Breaker point
Breaker point distributor
Breaker Point DistributorClick image to supersize
Breaker Point Distributor

An older style of distributor which used breaker points to act as an on-off switch to interrupt current flow through the primary winding of the coil. It also incorporated a rotor arm and condenser. In modern vehicles, it is replaced by a breakerless distributor and is usually called Electronic ignition system.

Breaker points

Breaker pointsBreaker Points

A mechanical switch in the distributor with two metal Contact points (usually made of silver, Platinum, or tungsten) that open and close. When the points are closed, energy is stored in the Primary windings of the Coil. When the breaker points open, this energy is transferred to the secondary windings of the coil and stepped up, resulting in a high voltage to fire the plugs. The Air gap between the breaker-point surfaces is critical. If the gap is too small, the timing is retarded, if too wide advanced. Also called points, Contact points, and ignition points.

Breaker strip
Strip of wood or plastic used to cover joint between outside case and inside liner of refrigerator.
Breaker’s yard
A British term for a salvage yard.
Breaker-triggered transistorized ignition
A transistorized ignition system whose distributor is the same as that of a coil ignition system, but whose contact breaker switches only the control current of the transistor, not the primary current. Usually not fitted as original equipment.
In fusion, situation when the power produced exceeds the power input for heating and confinement.
Break in


Period of operation between the installation of new or rebuilt parts and the time in which the parts are worn to the correct fit, driving at a reduced and varying speed for a specified mileage to permit parts to wear to the correct fit. British term is run-in.
Breaking capacity
The capacity of a switch, circuit breaker, or other similar device to break an electric circuit under certain specified conditions.
Breaking piece
An easily replaceable member of a machine subject to sudden overloads, made weaker than the remainder, so that in breaking it protects the machine from extensive damage.
Braking radiation
Breaking stress
The stress necessary to break a material, either in tension or compression.
Break-in oil
Special formulated oil used in a new engine for a specified amount of time so that all bearing surfaces, etc. are properly seated.
Break jack


Break one-oh
Trucker slang for ‘I want to talk (on channel 10)’ as in ‘Can I get a break one-oh?’
Break-out box
(BOB) A service tool that tees-in between the computer and the multi-pin harness connector. Once connected in series with the computer and the harness, this test device permits measurements of computer inputs and outputs.
The area of a dent in a panel where the sheet metal is actually buckled into the opposite direction of its normal shape.
Breakover angle
Break time
The length of time the contact breaker points remain open. Opposite to Dwell
Break up
British term for dismantling a vehicle and selling the parts. Similar to Part out
  1. Plates fitted on a forward weather deck to form a V-shaped shield against water that is shipped over the bow.
  2. A natural or artificial coastal barrier serving to break the force of the wave so as to provide safe harborage behind, it differs from the bulwark in that it has the sea on both sides of it.
An inclined stone paving of piers and breakwaters, designed to take the force of impact of the waves.
Breast Cap
A small plate on top of a bulwark, at the stem of a vessel to stiffen the bulwark.
A triangular plate bracket joining port and starboard side stringers at the stem.
To administer a breathalyzer test.
A device into which a driver blows to determine the amount of alcohol in his breath (and thus in his blood)
Breathalyzer test
A test given by the police to determine if a driver has exceeded the allowable alcohol content in his system.
A vent in the crankcase for relieving internal pressure or admitting air.

Breather pipe
A vent or pipe opening into the interior of the engine. It is used to assist ventilation the pipe usually extends downward to a point just below the engine so that the passing air stream will form a partial vacuum thus assisting in venting the engine.

Breather port
The small passage between the master cylinder fluid reservoir and the area behind the primary cups of the pistons. This port allows fluid from the reservoir to fill the area behind the cups when the brakes are applied, which prevents air bubbles from traveling around the lips of the primary cups as the brakes are released.

The action of taking in air for combining with fuel for burning as energy and then exhausting it.

Breathing capacity
The volume of air that enters the cylinder during each Intake stroke. Volumetric efficiency is determined by comparing the actual volume of air with the maximum possible amount. Also called air capacity.
Breath test
Bredig’s arc process
A process for making colloidal suspensions of metals in a liquid by striking an arc in the liquid between two electrodes of the metal.
Breech block
A movable block used for closing and opening an aperture, originally in guns but now also in machines.
Space in hot water or steam boilers between the end of the tubing and the jacket.
Fusion reactor in which further fuel (tritium) is bred from lithium Blanket surrounding the fusion chamber.
Breeder reactor
A fission reactor which produces more fissile material than is consumed in its operation.
Breeding ratio
The number of fissionable atoms produced in fertile material per fissionable atom, destroyed in a nuclear reactor. Symbol b r . The quantity b r -1 is known as the breeding gain.
Electromagnetic radiation emitted when a charged particle changes its velocity. Thus when electrons collide with a target and suffer large decelerations, the X-radiation emitted constitutes the continuous X-ray spectrum. From the German for braking radiation.
Literally, the word means certificate, patent, or diploma in French. In Randonneuring, it means two things certification of having successfully done a randonné, and the long-distance bicycle event itself of at least 200 kilometres. Brevet and Randonnée are often interchangeable terms, but a randonnée might be considered to be less structured or less formal than a brevet.
A vehicle brand of which all 1934-1936 models and all Heart Front models with required application are classic cars.
Abbreviation for British Racing Green
Bricklayer hammer
A special hammer for chipping cement blocks and bricks.
A dealer’s colloquial term for a vehicle purchaser’s house that is used as collateral for a loan toward the purchase of a vehicle.
  1. A metal support which is installed in the valve slot of a wheel rim and prevents the flap and tube from bulging through the slot under high pressure and high heat conditions. Also called lemna.
  2. A large horseshoe-shaped device that rides on side rails over a clay model. It is used to take reference points and make accurate measurements of the model.
  3. Circuit often used for measurement of the impedance of passive components, for both ac and dc. Four arms of the bridge are arranged in a diamond-shaped configuration, three comprising accurately known impedances and the fourth, the unknown. A voltage supply is connected to two opposite corners of the diamond and a detector between the other two. By adjusting the known component values, the bridge is balanced when the detector shows a null signal and equations are then available for the unknown in terms of the other three arms of the bridge.
  4. A structure spanning a river, road, etc. giving communication across it so that a vehicle or pedestrian can pass over. Includes overpasses, on-ramps, as well as other roadway structures over waterways.
Bridge bearing
A designed pad upon which the bridge beams rest to accommodate esp. horizontal thermal expansion and contraction. Usually a steel plate on steel rollers or a laminated structure of steel plates sandwiching blocks of rubber.
Bridge bolts
High-strength bolts used to fasten together the halves of a split brake caliper.
Bridge classification
Bridge structures can be classified into five groups, each of which imposes loads on their materials in different ways.
An electrical circuit in which two circuit branches (usually in parallel with each other) are connected with a third branch.


Bridged port
A vertical division in a two-stroke engine cylinder port which allows the use of a large port without danger of the ring or piston catching.
Bridge deck
The concrete horizontal platform or road surface extending the full length and width of the bridge.
Bridge end panels
Reinforced concrete roadway that acts as transition between a bridge and the road.
Bridge Formula
A bridge protection formula used by federal and state governments to regulate the amount of weight that can be put on each of a vehicle’s axles, and how far apart the axles (or groups of axles) must be to legally carry a given weight.
Bridge fuse
A fuse in which the fusible wire is carried in a holder, supported by spring contacts at its two ends; it is thus easily removable for renewing the fuse wire.
Bridge gauge
A measuring device for directing the relative movement of two parts of a machine due to wear at bearings, etc.
Bridge hanger
A form of hanger of small vertical dimensions, for supporting the overhead contact-wire of a traction system under bridges or tunnels.
Bridge igniter
A device for detonating the air bag.
Bridge Maintenance
Periodically recurring work designed to preserve an existing bridge. Work may be washing, painting, and sealing wood or concrete elements.
Bridge Major Rehabilitation
Reconstruction of a bridge, which upgrades and retains significant elements of the old, such as abutments, beams, or trusses.
A portable instrument for measuring large resistances on the Wheatstone-bridge principle. A megger contains a source of emf and the instrument dial on which the balance is indicated.
Bridge oscillator
Oscillator in which positive feedback and limitation of amplitude is determined by a bridge, which contains a quartz crystal for determining the frequency of oscillation. Devised by Meachan for high stability of operation in crystal clocks, etc.
Bridge rails
Steel or reinforced concrete barrier built into the full length of the bridge to prevent vehicles and pedestrians from going over the edge.
Bridge Replacement
Construction of a new bridge, where no structural elements of the old are incorporated into the new.
Bridges and materials
The dependence of the length of the span of a bridge on the strength of materials.
Bridge transition
A method, employed in connection with the series-parallel control of traction motors, in which the change from series to parallel is effected without interrupting the main circuit, and without any change in the current flowing in each of the motors.
Bridge washer
A protective thin metal washer installed at the valve stem between the flap and rim base to prevent the tube and flap from protruding through the valve slot as a result of high pressure and high temperature.
A characteristic of undercoats that occurs when a scratch or other imperfection in the surface isn’t completely filled. Usually due to under-reducing the primer or using a solvent that dries too fast.

  1. A portion of an overhead contact-wire system. It extends longitudinally between supporting structures and is attached at intervals to the contact-wire, in order to retain the latter in its proper lateral position.
  2. A rope or cable attached to two points (usually the right and left chassis members) of a vehicle and converging to a point of attachment for a tow rope.
A lustrous, shiny finish. Opposite to Matt
Bright annealing
The heating and slow cooling of steel or other alloys in a carefully controlled atmosphere, so that oxidation of the surface is reduced to a minimum and the metal surface retains its bright appearance.

Bright emitter
A thermionic valve with a pure tungsten cathode, heated by a DC current to 2600K in order to emit electrons. Originally used on all thermionic valves; now superseded by treated cathodes which emit at much lower temperatures.
An addition agent added to an electroplating solution to produce bright deposits.
As a quantitative term, brightness is deprecated.


Brightness control
Control which alters the brightness on a cathode-ray tube.

Bright plating
The production of a fairly bright deposit from an electroplating plant. Such surfaces require little finishing.
Headlights on high beam.
Chrome or stainless steel moldings, surrounds, etc.
The presence of considerable numbers of high harmonics in musical tone, or the enhancement of these in sound reproduction.
Brillouin formula
A quantum mechanical analogue in paramagnetism of the Langevin equation in classical theory of magnetism.
Brillouin scattering
The scattering of light by the acoustic modes of vibration in a crystal, i.e., photon-phonon scattering.
Brillouin zone
Polyhedron in k-space, k being the position wavevector of the groups or bands of electron energy states in the band theory of solids. Often constructed by consideration of crystal lattices and their symmetries.
Water saturated with a chemical such as salt, often used as an agent to pre-wet salt before applying it to icy roads

A type of wear in bearing components that is a series of dents in the races or cups
Brinell hardness
A test of a metal’s hardness by hydraulically pressing a hard ball into the metal.
Brinell hardness test
A method of measuring the hardness of a material by measuring the area of indentation produced by a hard steel ball under standard conditions of loading. Expressed as either Brinell hardness number (BHN) or, preferably, BH following the number, which is the quotient of the load on the ball in kilogram force divided by the area of indentation in square millimetres.
Brine recycling
Britannia metal
Alloy series of tin (80-90%) with antimony, copper, lead, or zinc, or a mixture of these.
British Association
(BA) A term used to describe a series of fine, small diameter threads for electrical and precision equipment.
British Association screw-thread
(BA thread) A system of symmetrical vee threads of 47.5° included angle with rounded roots and crests. It is designated by numbers from 0-25, ranging from 6.0 to 0.25mm in diameter and from 1 to 0.07mm pitch. Used in instrument work, but now being superseded by standard metric sizes. Even numbers are preferred sizes.
British Leyland
British LeylandClick image for books on
British Leyland

(BL) A former manufacturer of British automobiles, now called the Rover Group. Includes such models as the following:

British Motor Corporation
(BMC) A former manufacturer of British automobiles which changed its name to British Leyland and then to the Rover Group.
British Racing Green
(BRC) A dark green color which used to be the official racing color for British cars.
British Standard brass thread
A screw-thread of Whitworth profile used for thin-walled tubing. It has 26 threads per inch for each diameter.

British Standard Fine
(BSF) The fine screw thread used on most British vehicles before metrication. The coarse thread was British Standard Whitworth
British Standard pipe thread
(BSP thread) A screw-thread of Whitworth profile, but designated by the bore of the pipe on which it is cut (e.g., 3/8 in gas) and not by the full diameter, which is a decimal one, slightly smaller than that of the pipe. Also called British Standard Whitworth thread.
British Standards Institution
(BSI) An organization which prepares and issues British standard specifications.
British Standard specification
(BSS) A specification of efficiency, grade, size, etc., drawn up by the British Standards Institution, referenced so that the material required can be briefly described in a bill or schedule of quantities. The definitions are legally acceptable.
British Standard Whitworth
(BSW) A coarse screw thread used on British vehicles before metrication. It has a profile angle of 55° and a radius at root and crest of 0.1373 x pitch; 1/6 of the thread cut-off. The pitch is standardized with respect to the diameter of the bar on which it is cut.
British Standard Wire Gauge
British thermal unit
(BTU) A measurement of the amount of heat required to raise the temperature of one pound of water, one degree Fahrenheit (usually taken as 60° to 61°F). Equivalent to 252 calories, 778.2 ft-lbf, 1055J. 105 Btu=1 therm.
Brittle fracture
Fracture which occurs with no discernable plastic deformation, i.e., in the elastic region of the stress-strain curve. Caused by propagation of a crack as distinct from yielding. In metals it may be either intergranular or by cleavage along certain crystal planes.
The tendency to brittle fracture, i.e., without significant plastic deformation. Loosely used as the opposite of toughness, but more precisely means having low values of toughness or resistance to fracture.

Brittle point
A low extreme temperature at which a substance (like rubber) fractures on sudden impact.
Brittle temperature
Point at which a material changes in fracture behavior, from ductile to brittle. For polymers, it is often a little below Tg. Sometimes denoted TB. Sensitive to sample geometry (e.g., stress concentrations) and rate effects, such as occur in impact tests.
  1. Bringing a metal surface to the desired shape by forcing (pushing or pulling) a multiple-edged cutting tool across the surface.
  2. A metal cutting tool for machining holes, often non-circular; it consists of a tapered shaft carrying transverse cutting edges, which is driven or pulled through the roughly finished hole.
A generating process whereby metal is removed with a multiple-point tool, usually a bar, with tooth height increasing from the starting end. When the broach is pulled or pushed through or over the work, each tooth removes a clip of uniform thickness, in contrast to a milling cutting tooth which removes a wedge-shaped chip.
B road
  1. A road designation used in Britain
    • They are narrower than A roads.
    • They may be in the open or have dense foliage right up to the edge of the road.
    • May have very few road markings for curves, etc.
Broad-Based dip
A surface drainage structure specifically designed to drain water from an access road while vehicles maintain normal travel speeds.
Broad-base tower
A transmission line tower with each leg separately anchored.
Broad gauge
A railway gauge in excess of the standard 4 ft 8½ in (1.435 m). In particular, the gauge of 7 ft (2.134 m) laid down by Brunel but also the standard gauges of e.g., India,Russia, and Spain.
A condition in which a new engine has overcome any Wear-in problems.
Broken storage
The spaces between and around cargo packages, including dunnage, and spaces not usable because of structural interference.
  1. A person with legal authority to operate on behalf of the manufacturer.
  2. A person who arranges interstate movement of goods by other carriers.
  3. A person who arranges exempt loads for owner-operators and/or carriers.
  4. A person who arranges the buying or selling of goods for a commission.
  5. A person who leases owned equipment to a carrier.
An alloy of copper and tin; but now applied to other alloys not containing tin, e.g., aluminum bronze, manganese bronze, and beryllium bronze.

Bronze welding
  1. A closed car for two or four people
  2. A car with a closed in passenger compartment behind an open driver’s seat.
  3. A vehicle with doors and a roof–also known as a Coupe Chauffeur and a Coupe Limousine. ‘Panel Brougham’.
Brough Superior
A vehicle brand of which the pre-1948 models with required application are classic cars.
  1. A small inclined ramp to allow passage of trucks over a hatch coaming or bulkhead door sills etc.
  2. A raised or protruding area above or around an arch, like a headlamp or wheel well.
  3. A watershed over an airport
  4. The top of a hill on a road
Brown and Sharpe wire gauge
(B and S wire gauge) A system of designating the diameter of wire by numbers; it ranges from 0000 (0.46 in) to 50 (0.001 in).
Brownian movement
Small movements of bodies such as particles in a colloid, due to statistical fluctuations in the bombardment by surrounding molecules of the dispersion medium. It may be directed by movement of a galvanometer coil. Also called Brownian motion and colloidal movement and pedesis.
The result of a vehicle salesperson who sells a car to a customer in response to putting notes (like ‘call me about trading your car’) on car windows along the street.
Any tire injury which weakens, breaks, or separates the carcass cords without damaging the visible rubber surface.
  1. A paintbrush.


  2. The pieces of carbon, graphite, or copper, that rub against the Commutator on the Generator or starter motor or against the slip rings on an Alternator and conducts current from the power supply to the armature windings. As they wear down, they need to be replaced.
  3. A rubbing contact on a commutator, switch, or relay. Also called wiper.
Brush barrier
A sediment control structure created of slash materials piled at the toe slope of a road or at the outlets of culverts, turnouts, dips, and water bars.
That portion of the brush-holder of an electrical machine in which the brush slides or in which it is clamped.
Brush contact
Brush curve
The voltage drop between the brush arm and the segment beneath the brush at points along the brush width plotted against brush width as an indication of the correctness of compole flux density in a DC machine.
Brush discharge
Discharge from a conductor when the potential difference between it and its surroundings exceeds a certain value but is not enough to cause a spark or an arc. It is usually accompanied by hissing high noise. Also called brushing discharge and corona.


Brush gear
A general term used to denote all the equipment associated with brushes of a commutating or slip-ring machine.
Brush holder
A device which keeps the carbon brushes in an electric motor in contact with the commutator or slip ring.


Brush-holder arm
The rod or arm supporting one or more brush holders. Also called brush spindle or brush stud.
Brushing discharge
Brush lead
Brush plating
Method in which the anode carries a pad or brush containing concentrated electrolyte or gel which is worked over the surface to be plated. Similar methods are used for brush polishing
Brush rocker
A support for the brushes of an electrical machine which enables them to be moved bodily around the commutator.
Brush-rocker ring
Brush shift
The amount by which the brushes of a commutating machine are moved from the center of the neutral zone. Also called brush lead.

Brush spindle
Brush spring
A spring which pushes against the back end of a carbon brush in an electric motor to force it against the commutator or slip ring.
Brush stud
Abbreviation for the Birmingham Small Arms Company. A motorcycle manufactured in Britain from 1919-72.
BSB thread
Abbreviation for British Standard brass thread
Sheet metal screw with a blunt point with more threads per inch and smaller thread depth than type-A screws
Abbreviation for British Standard Fine
Abbreviation for Brake Specific Fuel Consumption — the ratio of the engine fuel consumption to the engine power output (as measured at the flywheel). BSFC has units of grams of fuel per kilowatt-hour (g/kWh) or pounds mass of fuel per brake horsepower-hour (lb/bhp-hr). BSFC is a measure of engine efficiency.
Abbreviation for British Standards Institution
BSP thread
Abbreviation for British Standard specification
Abbreviation for Backfire Suppressor (Ford)
Abbreviation for British Standard Whitworth
Abbreviation for Before top dead center. spark occurs on the compression stroke, before the piston reaches Top dead center.
B thread
Colloquial term for a truck tractor pulling two semi trailers where the second trailer sits on a fifth wheel that is permanently attached and extends off the rear of the lead trailer. Most commonly used on flatbeds or tank trailers. The B-train is considered a more stable double trailers configuration.
  1. Abbreviation for Battery Temperature Sensor
  2. Abbreviation for Bureau of Transportation Statistics. An organization which compiles, analyzes, and publishes statistics relevant to the US nation’s transportation system. Created to improve the knowledge base for public decision-making and to improve public awareness of the nation’s transportation system, BTS collects information on transportation and other areas as needed. The Bureau’s largest data collection programs are the Commodity Flow Survey and the American Travel Survey, conducted jointly with the Bureau of the Census to identify where freight and people go by all modes of transportation.
Abbreviation for Brake Transmission Shift Interlock
  1. Abbreviation for British thermal unit. The amount of heat that must be added to one pound of water to raise its temperature one Fahrenheit degree.
  2. Abbreviation for Board of Trade unit equal to 1 kWhr.
  1. Industry term referring to the group of aromatic hydrocarbons benzene, toluene and xylene
  2. Abbreviation for benzene, toluene, xylene
  1. A small blister in the finish of paint.
  2. The bubble of air and spirit vapor within a Level tube loosely, the level tube itself.
Bubble car
A type of small car which was popular in the 1950s. It had a bulbous-shaped glass front to provide maximum interior room in spite of its small size. The door opened to the front of the driver. Examples are the BMW Isetta and Heinkel Trojan.
Bubble film
Duplex polymer film with regular array of bubbles thermoformed into one side, used for crush-proof packaging.
Bubble pack
Bubble stabilization
Tendency of polymer bubble blown after extrusion in manufacture of film to maintain a constant shape without breaking or collapsing. Depends on tension stiffening behavior of molten polymer.
Bubble Wrap
Sheet of plastic with a series of small air bubbles used as packing material.
A vehicle brand of which the TAV 8, TAV 30, TAV 12 and Double Huit models with required application are classic cars.
Buchholz relay
A protective relay for use with transformers or other oil-immersed apparatus; it embodies a float which becomes displaced and operates the relay contacts if gas bubbles are generated by a fault within the equipment being protected.
Buchmann-Meyer effect
The special type of reflection of light from the sound-track on a disk record whereby the lateral velocity of the track can be determined.
In the design process of creating a vehicle, a buck is an accurate representation of only the vehicle’s interior which includes the seats, pedals, instruments, steering wheel, doors, and floor in order to evaluate style, ergonomics, comfort, function, etc.

Bucket conveyor
A conveyor or elevator consisting of a pair of endless chains running over toothed wheels, and carrying a series of buckets which, on turning over, discharge their contents at the delivery end.
Bucket seat

Bucket SeatBucket Seat

An individual seat which is found in pairs in the front of a vehicle. Named because the curvature of the backrest and cushion resembles a cut-out bucket.

Bucket tappet

Bucket tappetBucket Tappet

Valve lifters that are hollow, cylindrical, and closed at one end and used with some overhead camshafts. The flat, closed end of the tappet (bottom of the bucket) rests against the camshaft lobe with part of the Valve spring and Valve stem enclosed by the cylinder. Called bucket tappets because they are shaped like upside-down buckets.

Bucket valve
A non-return (delivery) valve fitted in the bucket or piston of some types of reciprocating pump
Bucket coil
A winding on an electromagnet to oppose the magnetic field of the main winding. Such a device is sometimes used in electromagnetic loudspeakers to smooth out voltage pulsations in the power supply. Also called hum-bucking coil.
  1. A locking clasp usually found on seat belts and tie-down straps.
  2. A metal strap
  3. In foundry work, a swelling on the surface of a sand mold due to steam generated below the surface.
  4. To crumple up, especially when metal bends in a vehicle accident. To twist or bend out of shape such as when plates of metal or a structural member deforms under compressive load.
Buckled plates
Battery plates that have been bent or warped out of a flat plane.
A portable cover secured over the deck opening of the hawsepipes and the chain pipes to restrict the flow of water through the openings.
Buckle up
To put your seat belt on. British term is belt up
Buckley gauge
A sensitive ionization gauge for measuring very low gas pressures.
  1. A distortion of accumulator plates caused by uneven expansion, usually as a result of heavy discharges or other maltreatment.
  2. Mode of deformation in which an elastic instability occurs in a plate or a structural member under compressive load, resulting in a twisting or bending out of shape. Usually leads to plastic deformation and eventual collapse.
  3. A term in reactor diffusion theory giving a measure of curvature of the deutron density distribution. The geometric buckling depends only on the shape and dimensions of the assembly while the material buckling provides a measure of the multiplying properties of an assembly as a function of the materials and their disposition.
Buck transformer
Transformer with secondary in mains circuit to regulate voltage according to a controlling circuit feeding the primary. Also called boost transformer
Abbreviation for Before upper dead center’. Same as BTDC.
Budd mounting
Budd wheel
A ten-hole, stud-piloted disc truck wheel originally designed by the Budd Corporation.
  1. To polish.
  2. A revolving disk composed of layers of cloth charged with abrasive powder; used for polishing metals.
  3. An expert in a field or a person greatly interested in the field as in Jim is a car buff.


Buff contour
The specked shape of a buffed retread tire.
Buffed crumb
Flakes of rubber produced by abrading treads of worn tires for retreading; of limited use as recycled material for new tire compounds.
  1. A machine used to Rasp the old tread from the tire.
  2. An electronic amplifier, often with unity gain, which is designed to decouple input from output. Normally designed to have high input impedance so that it does not load the driving stage and low output impedance such that it can provide current drive.
  3. A spring-loaded pad attached to the framework of railway rolling-stock to minimize the shock of collision; any resilient pad used for a resilient purpose. May be hydraulically controlled or dampened.
  4. A substance added to an electrolyte solution which prevents rapid changes in the concentration of a given ion. Also called buffer reagent
Buffer battery
A battery of accumulators arranged in parallel with a DC generator to equalize the load on the generator by supplying current at heavy-load periods and taking a charge during light-load periods
Buffer capacitor
Buffer circuit
The resistance-capacitor unit which determines the rate of rise or fall of the envelope of the waveform of emitted sounds which has been generated in electrostatic circuits in electronic organs.
Buffered radius
A dimension that ensures the proper contour of the buffed surface according to tire size and type and matrix dimensions.
Buffer reagent
A substance added to an electrolyte solution which prevents rapid changes in the concentration of a given ion. Also called buffer.
Buffer spring
The part lending resiliency to railway buffing gear.


Buffer tank
A closed tank that cushions the explosive expulsion of liquid from a system connected to it by controlling the gas pressure in the tank.
Buffet boundary
The limiting values of the speed of sound and altitude at which an aircraft can be flown without experiencing buffet in unaccelerated flight.
  1. Severe, pulsating force of wind. When you drive in a convertible with the top down, you will often experience this buffeting action of the wind. It is also noticeable when a vehicle is driven quickly with the windows down.
  2. An irregular oscillation of any part of an aircraft, caused and maintained by an eddying wake from some other part; commonly, tail buffeting in the downwash of the main plane, which gives warning of the approach of the Stall.
  1. Smoothing and polishing a surface by using a Buffing wheel and polishing paste or liquid.
  2. Grinding or Rasping off remaining tread rubber to give the Casing proper texture to accept new retread stock and proper dimensions to fit the matrix.
Buffing template
A machined device of a specific shape used to obtain the required Buffed contour.
Buffing wheel
A disc which is covered in soft cloth or lambswool. It is powered by a tool like a drill which spins the disc to give a high gloss shine to the surface of a vehicle.
Buff line
The dividing line in the cross section of a tire between the buffed surface of the original tire and the new retread rubber.
Abbreviation for Bicycle user group or bus user group to represent cyclists or bus travelers.
Bug and tar remover
A solution which will dissolve bugs and tar residue. After application, it needs to be washed off or it will also remove the paint.
BugattiClick image for books on

A vehicle brand of which all pre-1948 models (except types 52 and 68) are classic cars. The 1951 Type 101 model is a milestone car.

Bug deflector
Honda AccordClick image to supersize
Bug Deflector

A length of clear plastic which is attached to the front of the hood to prevent bugs from hitting the windshield. Also called a bug shield.

Bug out
Trucker slang for leaving a CB radio channel as in ‘I better bug out and get some shut eye.’
Bug shield
BuickClick logo for books on

A vehicle manufacturer which began in 1906 and is now part of General Motors . The 1931-32 series 90 and Limited with required application are classic cars. The Riviera for 1949 and 1963-70 are milestone cars. The 1953-54 Skylark are also milestone cars. Models include the following:

  1. A change from the standard process assembly of a vehicle specified by the VIN
  2. The thickness of the paint film deposited on the body during spraying (measured in mils).
Build date code
A code which tells you what day, month, and year the engine was made. Expressed alpha-numerically and stamped somewhere on the block.
In retreading a tire, a machine used to apply tread rubber to a Casing.

Builders and Repairers Association
Building basin
A structure in which one or more ships may be built and floated by flooding the basin.
Building Materials cargo
Truck cargo containing bricks, blocks, cement in bags, insulation, drywall, paint, hardware, etc.
Building Slip
A place where a ship is built


Build outs
Curbs which extend from the side of the road into the lane to reduce traffic speed.
Build quality
The quality of workmanship and material composition in the construction of a vehicle.
Build up
  1. To increase the surface level of metal by welding more material on it (and later grinding it to shape) or by adding filler to it.
  2. To assemble or put something together.
  3. To add material to something.
  1. The amount a weld face is extended above the surface of the metals being joined.
  2. An excess of some material as in, ‘There was a buildup of carbon on the top of the piston.’
Built-up crankshaft
A crankshaft which is not cast or forged as one piece, but made of several different parts.
Build-up sequence
The order in which successive welding runs or beads are applied in joining thick plates to achieve maximum strength with acceptable stress from heat distortion.
  1. A round area for vehicle turnaround typically located at the end of a cul-de-sac street.
  2. An electronic device which gives off light by the heating of an element contained with a glass enclosure. The metal base which conducts the electricity may be a barrel with locating pins, or it may have small Filament wires protruding from the base. In some cases it is a tube with contacts at either end. When replacing bulbs, especially high intensity bulbs like halogen, be sure to avoid touching the glass. The oil from your fingers will cause the bulb to overheat and burn out quickly. If you do touch the glass, you need to clean it with alcohol and air dry it.
Bulb bar
A rolled, or extruded, bar of strip form in which the section is thickened along one edge.
Bulb blackening
The blackening of a light bulb; gradual blackening of conventional, i.e., non-halogen light bulbs, occurs as a result of metal vapor deposition on the glass envelope which reduces light emission; severe blackening indicates imminent bulb failure
Bulb holder
Bulb Hygrometer
Bulb Plate
A narrow plate which is reinforced on one long edge.
Bulb Temperature
Bulk cargo
Loose and unpackaged goods such as oil, coal, ore, woodchips, etc. sometimes referred to as aggregate cargo.

Bulk carrier
A ship designed to carry unpackaged cargo such as grain, woodchips, ore, coal, etc.
Bulk charging
Using large containers of refrigerant to charge the system. Commonly employed with charging stations to perform complete system charges.
Bulk freight
Loose goods (like woodchips, grain, petroleum, ore, and coal) that are not packaged in a box, bottle, etc.
  1. A structural partition that separates compartments. This is generally a metal wall that extends from one side of a vehicle to the other. In the engine compartment, you would find a radiator bulkhead near the front and a firewall bulhead near the back of the engine bay. Another bulkhead separates the passengers from the trunk. The instrument panel is also a bulkhead.
  2. In a public service vehicle (i.e., taxi, limo), the partition which separates the driver from the passengers.
  3. Vertical partition walls which separates the interior of a ship into compartments or rooms.
  4. In an airplane fuselage, the major structural transverse dividing wall providing access between several internal sections, or a strengthened and sealed wall at the front and rear designed to withstand the differential pressure required for pressurization.
  5. In a power plant nacelle, the structure serving as a firewall.
  6. A masonry or timber partition to hold back soil found in a tunnel or along a waterfront.
  7. A wall-like structure used at the front of a flatbed or back of the power unit to protect against damage from shifting cargo, or a wall inside any trailer that partitions the load.
Bulkhead connector
An OEM device used to connect wiring inside the vehicle body with wiring outside the body. Usually located at the bulkhead or firewall.
Bulkhead deck
The uppermost deck to which the transverse watertight bulkheads are carried.
Bulking factor
Ratio between the volume of loosely placed material and the same weight of material when compacted to a given specification.
Bulk refrigerant drum
A large (e.g., 10 lbs, 25 lbs, 30 lbs) container of refrigerant generally used in professional air conditioning service shops which employ charging stations to perform complete system charges.
Bulk sales
Wholesale sales of gasoline in individual transactions which exceed the size of a truckload.
Bulk station
A facility used primarily for the storage and/or marketing of petroleum products, which has a total bulk storage capacity of less than 50,000 barrels and receives its petroleum products by tank car or truck.
Bulk Storage
  1. The storage of product in a shipping container
  2. The storage of loose, unpackaged product
Bulk terminal
A facility used primarily for the storage and/or marketing of petroleum products, which has a total bulk storage capacity of 50,000 barrels or more and/or receives petroleum products by tanker, barge, or pipeline.
Bulk test
Test for materials having a high attenuation for use as a radiation shield.
Bulk Trailer
A truck trailer that carries bulk cargo like woodchips, grain, petroleum, ore, and coal
Bulk Truck
A straight truck that carries bulk cargo like woodchips, grain, petroleum, ore, and coal
Bull bar
The upward extension of a bumper to protect lights and the grille.


Trucker slang for a Mack truck as in ‘Who we got in that eastbound bulldog.’
A power-operated machine, provided with a blade for spreading and leveling materials.

Bullet-point pick hammer
Bull-headed rail
A rail section once used widely in the UK, having the shape roughly of a short dumb-bell in outline, but with unequal heads, the larger being the upper part in use.
Bull horn
A warning horn that sounds like the bellow of a bull or the moo of a cow.
Bullhorn handlebar

bullhornBullhorn bar

A bicycle handlebar that proceeds laterally through the center attaching bracket and then rises upward at each end.

  1. Gold or silver in bulk, i.e., as produced at the refineries, not in the form of coin.
  2. The gold-silver alloy produced before the metals are separated.
Bullion content
In parcel of metal of minerals being sold, where the main value is that of the base metal which forms the bulk of the parcel, the contained gold or other precious metal of minor value included in the sale.
Bull low
The lowest gear in a transmission. Some older transmissions listed their gears as bull low (used for getting out of a stuck condition or climbing a very steep hill), low or first (used for starting out from a stop or for climbing a moderate hill), second (used for town driving or slight hills), third (used for highway cruising).
The upright radiator shape of 1913-30 Morris Oxford and Morris Cowley cars and vans which resembled a bull’s nose. Also called Flatnose or Snubnose
A metal ring used in the construction of overhead contact wire systems for electric schemes; it forms the junction of three or more straining wires.
Bull Riveting
To drive in rivets with a high powered air or hydraulic machine.
BultacoClick image for books on

A motorcycle manufacturer

  1. Fore-and-aft vertical plating immediately above the upper edge of the sheer strake.
  2. A sea-wall built to withstand the force of the waves; in some cases the reinforcement of the natural Breakwater.

BumpBump Sign

  1. A slight rising of the pavement possibly caused by a frost heave and if severe enough will be indicated by a sign
  2. The upward movement of the wheels and suspension. Also called Jounce.
  3. The action of a vehicle dealer who increases the sale price of the vehicle, interest rate, monthly payments, etc.
Bump and rebound
The two stages of suspension movement requiring damping.


On early vehicles, a bumper was a separate metal bar or blade at each end of a vehicle to prevent damaging the main part of the vehicle from hitting an obstruction or being hit by another vehicle. In modern vehicles the bumpers are integrated with the body panels and is secured by hydraulic rams.

Bumper bar
A tubular bar or series of bars which are designed to protect the front of a vehicle.
Bumper blade
A flat bar which is designed to protect the front or rear of a vehicle.
Bumper bracket
A device to which the bumper is attached to the frame, body, or chassis.
Bumper filler
A small panel usually made of plastic which fits between the bumper and the body of the vehicle.
Bumper horn
A short bumper extension which is mounted vertically (i.e., perpendicular to the main bumper), usually one on each side of the bumper. The British term is overrider
Bumper insert
A rubber or plastic strip fitted to the width of a bumper to prevent scoring of the bumper.
Bumper iron
A Bumper bracket
Bumper jack

Bumper jackBumper jack

A device for lifting one corner of a vehicle to change a tire. Older cars used a long bar which fitted into a base. A device on the long bar had a hook which was placed in a strategic place on the vehicle. A lug wrench was inserted into the other end of the device and used to move the moveable part up the long bar thus lifting the vehicle.

Bumper Pan
Sheetmetal below the bumper to keep dirt and debris from entering the engine bay. Also called ‘modesty panel’ or ‘modesty skirt.’
Bumper panels
Bumper skirt
Bumper Spring
Bumper sticker
  1. A piece of rectangular paper with a sticky back which can be attached to the back of a vehicle to promote something
  2. Trucker slang for a car following too closely as in ‘Hey Charlie better watch out you got a bumper sticker on your backdoor.’
Bumper system
An energy-absorbing system with some type of deformable material including hydraulic cylinders which enable the bumpers to protect the vehicle from damage in low-speed impacts.
Bumper to bumper
  1. A traffic condition in which a line of vehicles are stopped one after the other or are moving very slowly.
  2. A way of expressing the entire vehicle from one bumper to the other.
The action of correcting damaged panels by pounding out the dent.
Bumping blade
An autobody tool used for slapping out slight dents (sometimes without a supporting dolly). It has slight serrations which hold the metal to avoid stretching. Also called a bumping file.
Bumping file
An autobody tool used for slapping out slight dents (sometimes without a supporting dolly). It has slight serrations which hold the metal to avoid stretching. Also called a bumping blade.
Bumping hammer
An autobody hammer used with a dolly for restoring a panel’s shape.

Bumping out
An autobody term in which a damaged panel is hit with a hammer until it is nearly the correct shape.
Bumping spoon
Bump rubber
Bump start
  1. A method of starting a manual transmission (not for automatics) vehicle by pushing it (especially down a hill) and letting in the clutch while in second gear and the ignition set to the on position.
  2. To start a car using a bump start.
Bump steer
When an uneven road surface causes a vehicle to steer or lose Directional stability, this is called bump steer. At the front, bump steer is associated with the tie-rod and linkage-arm relationship. It is caused by the method of locating the Rear suspension, the type of rear suspension, and the geometry of the various linkages. In race cars, bump steer is designed out of the suspension so that the handling is as precise as possible. In most cars it is present to some degree. In fact, it can be useful to allow engineers to design a small amount of Understeer or oversteer into the chassis.
Bump stop

Bump stopBump stop

  • A cushioning device, usually rubber, that limits the upward movement of the wheels and suspension to prevent metal-to-metal contact that could lead to suspension damage or failure. Also called jounce bumpers.
  • A condition of driving when the vehicle support springs are fully compressed.
Bunched conductors
Arrangement which velocity-modules and thereby forms bunches of electrons in the electron beam current passing through it. Bunching would be ideal if the bunches contained electrons all having the same beam velocity. Also called input gap.


Buncher gap


The process of forming a steady electron beam into a succession of electron groups, or bunches. The result of interaction between an alternating electric field at the mouth of a cavity and an electron beam passing close by.
Bunching angle
Transit delay or phase angle between modulation and extraction of energy in a bunched beam of electrons.
Bundle conductor
Two or more overhead line conductors, suitably spaced to avoid Brush discharge loss, forming a phase, replaces a single large conductor.
Bundled out
Trucker slang for Trailer is fully loaded as in ‘As bundled out as I am those hills will really slow me down.’
Bungee cord
A rubber tie down strap of various lengths (usually 10 mm diameter) with a metal hook on each end. Most are covered with fabric. The hooks are often plastic coated to minimize scratching. Some have an extra hook attached in the middle. Others are linked with a second cord to produce an X-shape. They are used to secure objects to a luggage rack.

Bungee net
A specialized bungee cord shaped in the pattern of 25 squares with plastic covered hooks on two opposite sides of the net. It is used to secure objects to a luggage rack.

  1. A set of vertical metal cradle brackets or posts mounted on a log truck or trailer to hold logs in place. Also called bolsters.
  2. A sleeper on a truck
  3. A built-in bed on a ship.
  1. Space where ice or cooling element is placed in commercial installations.
  2. A storage space for coal or oil fuel.
Bunker capacity
The capacity of a space in a ship used for carrying fuel. It is calculated at a fixed rate of stowage per unit volume, according to fuel, and allowances for obstructions are made in percentage.
Bunker Fuel Oil
Heavy, residual fuel oil used in ships.
Bunker fuels
Fuel supplied to ships and aircraft, both domestic and foreign, consisting primarily of residual and distillate fuel oil for ships and kerosene-based jet fuel for aircraft. The term international bunker fuels is used to denote the consumption of fuel for international transport activities. Note: For the purposes of greenhouse gas emissions inventories, data on emissions from combustion of international bunker fuels are subtracted from national emissions totals. Historically, bunker fuels have meant only ship fuel.
Fuel consumed by the engines of a ship.
Bunsen Burner
A maneuver in which an aircraft performs half an inverted loop, i.e., the pilot is on the outside where he experiences Negative g
  1. The ability of an object to float
  2. The lifting power demonstrated when an object is immersed.
  3. The apparent loss in weight of a body when wholly or partly immersed in a fluid, due to the upthrust exerted by the fluid.
Soviet space shuttle which undertook a successful unmanned flight in November 1988, later missions were cancelled due to funding problems
The load on an instrument transformer. It is usually expressed as the normal rated load in volt-amperes, or as the impedance of the circuit fed by the secondary winding.
A credit report on a customer who is about to purchase a vehicle.
Bureau of land management
(BLM) The United States government agency within the U.S. Department of the Interior which has divided trails into four classes

  • Type I is at least 213cm wide (enough for a family vehicle), paved, easy to traverse.
  • Type II is also at least 213cm wide, not paved, but is usually improved. However it may be rough or rutted and contain Washboards. It is best traveled by high-clearance 4WD vehicles.
  • Type III is a narrow unimproved dirt road, often with rocks, steep hills, and mud over which only 4WD should use.
  • Type IV trails are for Mountain bikes, dirt bikes, and ATVs. 2WD or 4WD vehicles are not allowed.
Bureau of Transportation Statistics
(BTS) An organization which compiles, analyzes, and publishes statistics relevant to the US nation’s transportation system. Created to improve the knowledge base for public decision-making and to improve public awareness of the nation’s transportation system, BTS collects information on transportation and other areas as needed. The Bureau’s largest data collection programs are the Commodity Flow Survey and the American Travel Survey, conducted jointly with the Bureau of the Census to identify where freight and people go by all modes of transportation.
Burial site
Place for the deposition, usually in suitable containers, of radioisotopes after use, contaminated material or radioactive products of the operation of nuclear reactors. Also called graveyard.
Controlled firing of rocket engine for adjusting course and re-entry initiation.

Burned metal
A term occasionally applied to the metal which has been combined with oxygen to the end that some of the carbon has been changed into carbon dioxide and some of the iron into iron oxide.
Burnable poison
Neutron absorber introduced into a reactor system to reduce initial reactivity but becoming progressively less effective as burn-up proceeds. This helps to counteract the fall in reactivity as the fuel is used up. Boron-10, which is transmuted into helium by neutron capture, has been used in the form of borosilicate glass placed in empty control-rod guides.
Burned valves
Valves that have become pitted so that they do not close properly.
  1. A device which tends to consume a lot of material.
  2. Device in which burning of fuel takes place.
  3. A device for the final conveyance of the gas, or a mixture of gas and air, to the combustion zone.
Burner firing block
Unit made from refractory material that fits into a furnace wall at the burner position, having a nozzle-protecting recess at back and a tunnel on the firing side. It is called quarl in oil-firing practice.
Burner head
That portion of a burner beyond the outlet end of the mixer tube that contains the ports.
Burner loading
Potential heat that can be liberated efficiently from a burner. Expressed in kilowatts or Btu h-1
Burner turndown factor
Minimum gas rate at which a burner is capable of stable flame propagation without the flame flashing back to the air-gas mixing point or blowing off from the burner nozzle or head.
Burner valve
A manually or mechanically operated valve which permits control of the flow of fuel.
  1. The violent combination of oxygen with any substance to produce heat.
  2. The action of consuming something to produce heat, i.e., combustion.
  3. The heating of an alloy to too high a temperature, causing local fusion or excessive penetration of oxide, and rendering the alloy weak and brittle.
  4. The action of erosion or eating away. Electrical contacts are burning when they wear away; exhaust valves are burning when they pit and don’t close properly.
  5. Flame cutting.
  1. To bring a surface to a high shine by rubbing with a hard, smooth object.
  2. The process of breaking-in new brake pads or shoes so the linings conform to the disc or drum friction surfaces.
  3. The initial seating process in which the brake shoes or pads wear to conform to the exact contours of the brake drum or disc.
Burn mark
Molding defect found on polymer surfaces caused by adiabatic compression of gas trapped in mold cavity by advancing melt front
Sudden failure of any device, caused by excessive current, leading in turn to overheating; may also be due to failure of artificial cooling in any electronic assembly or sub-assembly.

Burnout velocity
The maximum velocity achieved by a rocket when all the propellant has been consumed.
Burn rate
Burn rubber
The action of rapid acceleration where the wheels make rapid rotation, but there is only very little Momentum. As a result, the driving wheels leave some rubber behind on the pavement.

Burnt metal
Metal which has become oxidized by overheating, and so is rendered useless for engineering purposes.
Burnt valves
  1. In nuclear fuel, amount of fissile material burned up as a percentage of total fissile material originally present.
  2. Of fuel element performance, the amount of heat released from a given amount of fuel, expressed as megawatt or gigawatt-days per tonne.
  1. A roughness left on a cut or punched metal. A sharp, rough edge or ridge esp. around a drilled hole.
  2. A small rotary tool with cutting teeth like a file used for metal removal.
Burred wheel
A wheel which has metal slivers or roughness around the edge of the rim.
Burr walnut
A wood veneer used for instrument panels and door trim on some cars.


  1. To explode and suddenly lose all the air in a tire.
  2. A defect, often very small, in fuel cladding or sheeting which allows fission products to escape.
  3. Unusually large pulse arising in an ionization chamber caused by a cosmic ray shower.
  4. Short period of intense activity on an otherwise quiet data channel.
  5. Sudden increase in strength of received radio signals caused by sudden changes in the ionosphere.
Burst-can detector
An instrument for the early detection of ruptures of the sheaths of fuel elements inside a reactor. Also called burst-cartridge detector or leak detector.
Burst cartridge
Fuel element with a small leak, emitting fission products. Also called burst slug.
Burst-cartridge detector
Burst slug
Bury the needle
Going beyond the displayed maximum speed. For example, an analog speedometer may show speeds from zero to 137 kph on its display. When the needle reaches the maximum displayed point, it does not rest there as the vehicle accelerates further. The needle is attached to a spring allowing the needle to keep winding up. The bezel around the speedometer may hide the needle so that it goes beyond the line of sight and is considered buried.
  1. A large public or private passenger vehicle used for transporting many (at least 10) passengers.
  2. The part of the payload of a space exploration vehicle which contains the atmospheric (re-)entry probes, or a universal platform for diverse space experiments and applications.
  3. A Bus-bar which is a heavy electrical conductor used to carry or make a mutual connection between several circuits.
  1. A heavy conductor used to carry or make a mutual connection between several circuits. Also called a bus.
  2. Length of constant-voltage conductor in a power circuit. Normally of rigid copper construction and located in a power station or substation.
  3. Supply rail maintained in a constant potential (including zero or ground) in electronic equipment.
Bus Boarder
Infrastructure to assist people to board a bus.
Bus-coupler switch
A switch or circuit breaker serving to connect two sets of duplicate bus-bars.
  1. British term for bushing.
  2. A hardened cylindrical inset in a drilling jig to position a drill or reamer accurately.
The operation of dressing the surface of stone or concrete with a special hammer having rows of projecting points on its striking face for decoration or to improve bonding to the next placement of further concrete.
  1. A protective liner or sleeve that cushions noise, friction, or movement. suspension bushings are often made from two pipes (one inside the other) with a sleeve of rubber in the space between the two pipes.
  2. Rubber bushings on the suspension system should be lubricated regularly.
  3. A bearing for a shaft, spring shackle, piston pin, etc., of one piece construction which may be removed from the part.
  4. An insulator which enables a live conductor to pass through a grounded wall or tank (e.g., the wall of a switch house or the tank of a transformer.)
  5. An internal component in a roller chain which the pin articulates around and the roller rotates on.
Business coupe
A basic low-end, two-door coupe. Often with only a front bench seat and no back seat. Favored by salesmen because the back could be loaded with samples.
Business end
A colloquial term for the part of something that actually does the work. For instance, the business end of a shovel is the part that contacts the ground, not the handle.
Business Route
(Bus Rte) An alternate road which leads through the center of a municipality where most of the ‘downtown’ business establishments are located.
A cable, extending the whole length of an electric train, which connects all the collector shoes of like polarity. Also called power line
Bus-line couplers
Plug-and-socket connectors to join the bus-line of one coach of an electric train to that of the next.
Abbreviation for Bus Negative — the negative terminal.
Bus Operators Charter
Document setting out standards of service provision.
Bus Operators Forum
Meeting group of local bus operators.
Abbreviation for Bus Positive — the positive terminal.
Bus Rte
Abbreviation for Business Route


A car body with an attached luggage compartment or the appearance of one such as seen on the 1982 Cadillac Seville.

Bustle pipe
Main air pipe surrounding blast furnace, which delivers low pressure compressed air to tuyères.
Bus-wire coupler
A flexible connection between the coaches of an electric train for maintaining the continuity of bus-wires which run throughout the train-length.
Busy intersection
A road junction where there is a lot of traffic and may be controlled by signal lights or not. Usually a place where accidents are more likely to occur.
A petroleum gas easily liquefied under pressure, recovered from natural gas. Used as a low-volatility component of motor gasoline, processed further for a high-octane gasoline component, used in LPG for domestic and industrial applications and used as a raw material for petrochemical synthesis. Often used as engine fuel in trucks.

Trade name for diethylene glycol dibutyl ether, used for separating uranium and plutonium from fission products.
Particular groups of atoms in organic compounds which have the effect of lowering frequency of the radiation absorbed by these compounds.
  1. The joint between two plates or other members which meet edge to edge.
  2. The square ends of a piston ring.
Butt connector
A solderless wire connector used to permanently join two wire ends together.
Butted tubing
Tubing whose outside diameter remains constant but whose thickness is reduced in midsection where less strength is needed.
Term used in metal extrusion where an open U shape is first made and the sides then folded closer to make a vertically sided U. This enables the die to be much stronger because the narrow section to form the inside of the U can have a wider base.

Butterfly controlled carburetor
A carburetor using a flat plate between the venturi and the intake manifold to regulate airflow.
Butterfly curve
The strain versus applied field curve of ferroelectrics.
Butterfly valve
A nut with wings to be turned by thumb and finger. Sometimes called a Wing nut.
Butterfly valve
  1. A small metal disc located in the carburetor that controls the flow of air into the carburetor. It is so named due to its resemblance to the insect of the same name.
  2. A disk turning on a diametral axis inside a pipe; used as a throttle valve in a gasoline engine.
  3. A valve consisting of a pair of semicircular plates hinged to a common diametral spindle in a pipe; by hinging axially, the plates permit flow in only one direction.
Trucker slang for beer as in ‘When I get home I’m gonna get me some buttermilk.’
butt joint
Butt joint
Butt joint
  1. A piston ring gap in which the two ends of the ring are squared off.
  2. A weld where the two panels are not overlapped but fit against each other end to end.


A colloquial term for a Cab-Over-Engine truck
  1. The distance away from the centerline
  2. An intersection of a molded surface with a vertical longitudinal plane.
Buttock planes
Longitudinal sectional planes drawn through a ship’s form; used for laying-off in the molding loft, and for calculation of volumes, etc.
A small disk or knob which activates something electrical when it is pressed such as a starter button.

Button Die
Small adjustable dies for screw machines and similar work, supported in a ring holder.
Button head
A bolt with a Round head
Button-headed screws
Screws having hemispherical heads, slotted for a screwdriver. Also called half-round screws
Button microphone
Small microphone which can be fitted in the buttonhole.


Button Socket Head Cap Screw

Button Socket Head Cap ScrewButton Socket Head Cap Screw

A socket cap screw with a wider dome-shaped head and lower profile than a socket cap screw. Used when a wider bearing surface or a smoother, more finished appearance is desired. Button head cap screws do not afford the strength of socket head cap screws and are designed for light fastening applications.

Butt Rally
  1. A thick rubber reinforcement in the shoulder of a tire. It provides support at the edge of the tread, limits shoulder area flexing, and protects the shoulder of off-road tires.
  2. A supporting pier built on the exterior of a wall to enable it to resist outward thrust.
Buttress screw-thread
A screw-thread designed to withstand heavy axial thrust in one direction. The back of the thread slopes at 45°, while the front or thrust face is perpendicular to the axis.
Buttressed thread
A screw thread with one vertical and one inclined flank.
Butt strap
A plate that overlaps two pieces that are pressed up against each other edge to edge (i.e., butted) in order to secure them. The two butted pieces may be welded to each other or the butt strap could be welded to the pieces or simply bolted to them.
Butt-welded tube
Tube made by drawing mild steel strip through a bell-shaped die, so that the strip is coiled into a tube, the edges being then pressed together and welded.
The joining of two plates or surfaces by placing them together, edge to edge, and welding along the seam thus formed.


A non-porous synthetic rubber used in making inner tubes and tubeless tire liners and as a base for one type of adhesive. It has poor resistance to petroleum oils and gasoline but excellent resistance to vegetable and mineral oils, and to such solvents as acetone, alcohol, phenol, and ethylene glycol. Also has excellent resistance to water and gas adsorption and sunlight.

Butyl Alcohol
Alcohol derived from Butane that is used in organic synthesis and as a solvent.

(C4H8) An Olefinic hydrocarbon recovered from refinery processes.
Butyl Ether
Butyl rubber
A synthetic rubber used as a base for one type of adhesive. It has poor resistance to petroleum oils and gasoline but excellent resistance to vegetable and mineral oils; to such solvents as acetone, alcohol, phenol, and ethylene glycol; and excellent resistance to water and gas adsorption and sunlight.
Butyl tube
The typical material for tubes. Inexpensive, easy to repair.
Buxton certification
The certification of the suitability of electrical equipment for use in an atmosphere in which fire or explosion hazards are present.
Buy at end-of term interest rate
The effective net interest rate for the lease if, at the end of the lease, the car is purchased at the end-of-lease purchase price.
Buying decisions
The act of determining whether or not a product purchase or repair, will be made, and/or which product or service will be purchased.
Buy rate
The interest rate that banks or financing institutions will charge on all vehicle contracts being financed. It is a secret number between the bank and the dealer which is the real amount of the interest rate that the loan starts out at before the dealer increases it for its own extra profit.
  1. Severe vibration of a control surface in transonic or supersonic flight caused by separation of the airflow due to compressibility effects.
  2. To interfere with an aircraft in flight by flying very close to it.
Abbreviation for Bowl vent
Abbreviation for Bowl vent port
Abbreviation for Bi-Metal Vent Control Valve
Abbreviation for Backpressure variable transducer
Black and white, usually referring to photographs.
Abbreviation for Blackwall, as in BW tires.
Abbreviation for Birmingham wire gauge.
Abbreviation for Boiling water reactor
Waterway dug round the side of a reservoir or dam to carry off surplus water from the streams entering it.
  1. A road which avoids the congested area of a city traffic.
  2. An alternate route for a flowing substance.
  3. To go around something to avoid it.
  4. A passage at one side of, or around, a regular passage
Bypass air screw
A screw located on the airflow sensor of a fuel injection system. It adjusts the amount of air allowed into the air-fuel mixture.
Bypass air solenoid
(BPA) A device used to control the idle speed on some fuel-injected vehicles.
By-pass capacitor
A capacitor having a low reactance for frequencies of interest connected in shunt with other components so as to short-circuit them for signal frequency currents.
Bypass filter
An oil filter that constantly filters a portion of the oil flowing through the engine.
Bypass ratio
The ratio of the by-pass airflow to the combustion airflow in a dual-flow turbojet having a single air intake.
Bypass Solenoid
Bypass System
Bypass turbojet
A turbojet in which part of the compressor delivery is by-passed around the combustion zone and turbine to provide a cool, slow propulsive jet when mixed with the residual efflux from the turbine.

Bypass valve
  1. (BPV) A valve that can open and allow fluid or gas to pass through in other than its normal channel.
  2. A switching device (Silicon-controlled rectifier or, in the past, mercury arc valve), connected across the converter switching devices of a high-voltage DC transmission system, normally not conducting but able to maintain flow of current whenever the main conducting devices have to be interrupted.
  3. A valve by which the flow of fluid in a system may be directed past some part of the system through which it normally flows, e.g., an oil-filter in a lubrication system.