ac·cel·er·a·tionakˌseləˈrāSH(ə)n/nounincrease in the rate or speed of something."the acceleration of the industrialization process"synonyms:hastening, precipitation, speeding up, quickening, stepping up,advancement, furtherance, boost, stimulation, spur MorePHYSICSthe rate of change of velocity per unit of time.a vehicle's capacity to gain speed within a short time."a Formula One car is superior to an Indy car in its acceleration"