decelerate
1. [ verb ] lose velocity; move more slowly
Synonyms: slow slow_down retard slow_up
Examples:

"The car decelerated"

Related terms: accelerate decrease delay slow deceleration
2. [ verb ] reduce the speed of
Synonyms: slow_down
Examples:

"He slowed down the car"

Related terms: accelerate retard moderate fishtail slowdown
Similar spelling:   deceleration