accelerator

noun

1. a person or thing that accelerates or increases the speed of something; specif.,
   1. a device, such as the foot throttle of an automobile, for increasing the speed of a machine
   2. a nerve or muscle that speeds up a body function
2. Chem. a substance that speeds up a reaction
3. Nuclear Physics a betatron, cyclotron, synchrotron, linear accelerator, or similar apparatus that accelerates charged particles to high energies: accelerators are used for experimental purposes
4. Photog. a chemical that speeds up developing