1. Anything that increases rapidity of action or function.
2. In physiology, a nerve, muscle, or substance that quickens movement or response.
3. A catalytic agent used to hasten a chemical reaction.
4. In nuclear physics, a device that accelerates charged particles (e.g., protons) to high speed in order to produce nuclear reactions in a target, often for the production of radionuclides or for radiation Therapy.
Origin: L. Accelerans, pres. P. Of ac-celero, to hasten, fr. Celer, swift
(chemistry) a substance that initiates or accelerates a chemical reaction without itself being affected.