Synset

become quiet or calm, especially after a state of agitation
<verb.emotion>   freq. cnt.: 6 freq. cnt.: 4 freq. cnt.: 1 freq. cnt.: 1

calm

calm down

chill out

cool it

cool off

settle down

simmer down

sample sentences

"After the fight both men need to cool off."
"It took a while after the baby was born for things to settle down again."