simmer down vs chill out

simmer down and chill out both are verbs.

Word	Noun	Adjective	Verb	Adverb
simmer down	No	No	Yes	No
chill out	No	No	Yes	No

As verbs, simmer down and chill out are synonyms defined as:

simmer down and chill out: become quiet or calm, especially after a state of agitation

Other synonyms of simmer down include calm, calm down, cool it, cool off, settle down.

simmer down (verb)	chill out (verb)
become quiet or calm, especially after a state of agitation	become quiet or calm, especially after a state of agitation