be quiet vs keep mum

be quiet and keep mum both are verbs.

Word	Noun	Adjective	Verb	Adverb
be quiet	No	No	Yes	No
keep mum	No	No	Yes	No

As verbs, be quiet and keep mum are synonyms defined as:

Other synonyms of be quiet include belt up, button up, clam up, close up, dummy up, shut up.

be quiet (verb)	keep mum (verb)
refuse to talk or stop talking; fall silent	refuse to talk or stop talking; fall silent