'acceleration' definitions:

Definition of 'acceleration'

From: WordNet
noun
An increase in rate of change; "modern science caused an acceleration of cultural change" [ant: deceleration, retardation, slowing]
noun
The act of accelerating; increasing the speed [syn: acceleration, quickening, speedup] [ant: deceleration]
noun
(physics) a rate of increase of velocity [ant: deceleration]