accelerator

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A device, especially the gas pedal of a motor vehicle, for increasing speed.
2. n. Chemistry A substance that increases the speed of a reaction.
3. n. Physics A particle accelerator.

Century Dictionary and Cyclopedia

1. n. One who or that which accelerates; a hastener. Hence— In England, a post-office van. In anatomy, a muscle, the accelerator urinæ, which expedites the discharge of urine. In photography: Any substance or device which shortens the time of exposure of a sensitized plate or paper to the light, in either the camera or the printing-frame. Any chemical which may be added to the developing solution to shorten the time necessary for development, or, by increasing the normal efficiency of the developer, to lessen the requisite time of exposure. An accelerating gun. See accelerate.
2. n. A device in a motor-car by which the operator may render inoperative the speed governor of the motor. If the governor is of the centrifugal type, as the speed increases the balls or weights fly outward against the action of a spring. The accelerator increases the tension of the spring or draws the balls inward directly, so that the governor ceases to act to close the throttle or regulate speed as the motor increases its number of revolutions above the limit set by the normal tension of the springs.

Wiktionary

1. n. One who, or that which, accelerates.
2. n. A device for causing acceleration.
3. n. chemistry A substance which speeds up chemical reactions.
4. n. vehicles An accelerator pedal.
5. n. photography A chemical that reduces development time.
6. n. physics A device that accelerates charged subatomic particles.
7. n. physiology, medicine A muscle or nerve that speed the performance of an action.
8. n. computing accelerator key

GNU Webster's 1913

1. n. One who, or that which, accelerates. Also as an adj..

WordNet 3.0

1. n. a valve that regulates the supply of fuel to the engine
2. n. (chemistry) a substance that initiates or accelerates a chemical reaction without itself being affected
3. n. a scientific instrument that increases the kinetic energy of charged particles
4. n. a pedal that controls the throttle valve