The Collaborative International Dictionary of English v.0.48:

Accelerator \Ac*cel"er*a`tor\, n.
   One who, or that which, accelerates. Also as an adj.; as,
   accelerator nerves.
   [1913 Webster]

WordNet (r) 3.0 (2006):

accelerator
    n 1: a pedal that controls the throttle valve; "he stepped on
         the gas" [syn: accelerator, accelerator pedal, gas
         pedal, gas, throttle, gun]
    2: a valve that regulates the supply of fuel to the engine [syn:
       accelerator, throttle, throttle valve]
    3: (chemistry) a substance that initiates or accelerates a
       chemical reaction without itself being affected [syn:
       catalyst, accelerator] [ant: anticatalyst]
    4: a scientific instrument that increases the kinetic energy of
       charged particles [syn: accelerator, particle
       accelerator, atom smasher]

The Free On-line Dictionary of Computing (19 January 2023):

accelerator

    Additional hardware to perform some function faster
   than is possible in software running on the normal CPU.
   Examples include graphics accelerators and floating-point
   accelerators.

   (1994-11-08)