Accelerator

[1] In automobiles, this is the "gas pedal" which is attached by linkage to the throttle in the carburetor or to the fuel injection system. It regulates the amount of fuel which is sent to the engine. In motorcycles, the accelerator is located on the right-hand twist grip or an actuating lever.
[2] A chemical which is added to something to make a process happen more quickly. For example, a chemical may be added to paint to cause it to dry faster. The opposite is "retarder". A material added to an adhesive to speed up its cure or to chemically convert the whole mass to a solid. Accelerators differ from catalysts in that they are a part of the chemical reaction and lose their chemical identity as a result.
[3] Any substance increasing the speed of the vulcanization process of rubber.
See also depress the accelerator, ease up on the accelerator, step on the accelerator, take foot off the accelerator