/ əkˌseləˈreɪʃn; NAmE / noun
[ U , sing. ] acceleration (in sth) an increase in how fast sth happens :
an acceleration in the rate of economic growth
[ U ] the rate at which a vehicle increases speed :
a car with good acceleration
[ U ] ( physics ) the rate at which the velocity (= speed in a particular direction) of an object changes
late 15th cent.: from Latin acceleratio(n-) , from accelerare hasten, from ad- towards + celer swift.