Antonyms of verb accelerate

2 senses of accelerate

Sense 1
accelerate, speed up, speed, quicken -- (move faster; "The car accelerated")
       Antonym of decelerate (Sense 1)
      => decelerate, slow, slow down, slow up, retard -- (lose velocity; move more slowly; "The car decelerated")

Sense 2
accelerate, speed, speed up -- (cause to move faster; "He accelerated the car")
       Antonym of decelerate (Sense 2)
      => decelerate, slow down -- (reduce the speed of; "He slowed down the car")

Synonyms/Hypernyms (Ordered by Estimated Frequency) of verb accelerate

2 senses of accelerate

Sense 1
accelerate, speed up, speed, quicken -- (move faster; "The car accelerated")
       => intensify, deepen -- (become more intense; "The debate intensified"; "His dislike for raw fish only deepened in Japan")

Sense 2
accelerate, speed, speed up -- (cause to move faster; "He accelerated the car")
       => change, alter, modify -- (cause to change; make different; cause a transformation; "The advent of the automobile may have altered the growth pattern of the city"; "The discussion has changed my thinking about the issue")