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1. A decrease in rate of change
   "the deceleration of the arms race";
   - slowing, retardation
    
2. (physics) a rate of decrease in velocity
    
3. The act of decelerating; decreasing the speed
   "he initiated deceleration by braking"

Derived forms: decelerations

Type of: alteration, change, hurrying, modification, rate, speed, speeding

Antonym: acceleration

Encyclopedia: Deceleration