slow down

Short definition from Wiktionary

Verb

1. 1
   To decelerate.
2. 2
   To reduce the velocity, speed, or tempo of something.
3. 3
   To become less intense, enthusiastic, etc., usually with a positive connotation, implying that one is stripped of exaggerated or unnecessary eagerness.

Noun

1. 1
   Alternative form of slowdown.