definition of
deceleration

[1] #1 deceleration n. [slowing, retardation] a decrease in rate of change; "the deceleration of the arms race". wn

[2] #2 deceleration n. (physics) a rate of decrease in velocity. wn

[3] #3 deceleration n. the act of decelerating; decreasing the speed; "he initiated deceleration by braking". wn