decelerate

v. i.	1.	to reduce speed; as, The car decelerated. Opposite of accelerate.
v. t.	1.	to cause to reduce speed. Opposite of accelerate.

Verb	1.	decelerate - lose velocity; move more slowly; "The car decelerated" Synonyms: slow, slow down, slow up, retard Antonyms: accelerate, quicken, speed up, speed - move faster; "The car accelerated"
	2.	decelerate - reduce the speed of; "He slowed down the car" Synonyms: slow down Antonyms: accelerate, speed up, speed - cause to move faster; "He accelerated the car"

accelerate, deceleration, decrease, delay, detain, diminish, fall, hold up, lessen, quicken, retard, retardation, slow, slow down, slow up, slowing, speed, speed up