decelerateEnglishOxford English Thesaurusdecelerate verb there is a whine coming from the gearbox every time I decelerate: slow down, slow up, slow, go slower, ease up, slack up, reduce speed, lessen one's speed, brake, put the brakes on, hit the brakes; British, informal slam on the anchors. ▷antonyms accelerate.decelerate Oxford Dictionary of English