Main Entry: de·cel·er·ate Pronunciation: (')dE-'sel-&-"rAt Function: verb Inflected Forms: -at·ed; -at·ing transitive senses : to reduce the speed of : slow down decelerateintransitive senses : to move at decreasing speed —de·cel·er·a·tion/(")dE-"sel-&-'rA-sh&n/noun