decelerate

from WordNet (r) 3.0 (2006)

decelerate
    v 1: lose velocity; move more slowly; "The car decelerated"
         [syn: {decelerate}, {slow}, {slow down}, {slow up},
         {retard}] [ant: {accelerate}, {quicken}, {speed}, {speed
         up}]
    2: reduce the speed of; "He slowed down the car" [syn:
       {decelerate}, {slow down}] [ant: {accelerate}, {speed},
       {speed up}]

from The Collaborative International Dictionary of English v.0.48

decelerate \decelerate\ v. i.
   1. 1 to reduce speed; as, The car decelerated. Opposite of
      {accelerate}.

   Syn: slow, slow down, slow up, retard.
        [WordNet 1.5]

from The Collaborative International Dictionary of English v.0.48

decelerate \decelerate\ v. t.
   to cause to reduce speed. Opposite of {accelerate}.

   Syn: slow down.
        [WordNet 1.5]

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