-ˌrād.ə(r), -ātə- noun
( -s )
1. : one that accelerates: as
a. : any muscle or nerve that speeds the performance of an action
cardiac accelerator
b. : a chemical (as an alkali) used in photography for speeding the action of a developer — called also activator
c. : any of several devices for increasing the speed of a motor vehicle engine ; especially : a foot-operated throttle that varies the supply of fuel-air mixture to the combustion chamber
d. : an attachment to a dry-pipe valve for accelerating its operation when sprinkler heads are opened
e. : a substance that speeds a chemical reaction ; especially : one that speeds the vulcanization of rubber or the curing of a plastic
f. : a substance added to stucco, plaster, mortar, concrete, or similar materials to hasten the set
g. : an apparatus for imparting high velocities by electromagnetic or electrostatic means to charged particles (as electrons) which are generated in the apparatus, accelerated in controlled paths to a state of high energy, and focused continuously until they emerge as a stream of high-speed projectiles — see cyclotron
2. : the ratio of increase or decrease in investment to an increase or decrease in income — called also acceleration coefficient ; compare acceleration principle