say it: ak-SEL-ur-ay-tur
accelerator is a noun meaning "a pedal that controls the throttle valve". It carries 4 recorded senses.
a valve that regulates the supply of fuel to the engine
(chemistry) a substance that initiates or accelerates a chemical reaction without itself being affected
chemistry
a scientific instrument that increases the kinetic energy of charged particles
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for accelerator come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.