abrasion test: The measurement of abrasion resistance, usually by the weighing of a material sample before and after subjecting it to a known abrasive stress throughout a known time period, or by reflectance or surface finish comparisons, or by dimensional comparisons.
abrasive belt: A cloth, leather, or paper band impregnated with grit and rotated as an endless loop to abrade materials through continuous friction.
abrasive blasting: The cleaning or finishing of surfaces by the use of an abrasive entrained in a blast of air.
abrasive cloth: Tough cloth to whose surface an abrasive such as sand or emery has been bonded for use in grinding or polishing.
abrasive cone: An abrasive sintered or shaped into a solid cone to be rotated by an arbor for abrasive machining.
abrasive disk: An abrasive sintered or shaped into a disk to be rotated by an arbor for abrasive machining.
abrasive jet cleaning: The removal of dirt from a solid by a gas or liquid jet carrying abrasives to ablate the surface.
abrasive machining: Grinding, drilling, shaping, or polishing by abrasion.
abreast milling: A milling method in which parts are placed in a row parallel to the axis of the cutting tool and are milled simultaneously.
abreuvoir: A space between stones in masonry to be filled with mortar.
absolute altimeter: An instrument which employs radio, sonic, or capacitive technology to produce on its indicator the measurement of distance from the aircraft to the terrain below. Also known as terrain-clearance indicator.
absolute altitude: Altitude above the actual surface, either land or water, of a planet or natural satellite.
absolute block system: A block system in which only a single railroad train is permitted within a block section during a given period of time.
absolute blocking: A control arrangement for rail traffic in which a track is divided into sections or blocks upon which a train may not enter until the preceding train has left.