shut up vs close up

shut up is an adjective but close up is not an adjective.

Word	Noun	Adjective	Verb	Adverb
shut up	No	Yes	Yes	No
close up	No	No	Yes	Yes

As verbs, shut up and close up are synonyms defined as:

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

shut up (adjective)	close up (adjective)
closely confined

shut up (verb)	close up (verb)
cause to be quiet or not talk	refuse to talk or stop talking; fall silent
refuse to talk or stop talking; fall silent	block passage through
place in a place where something cannot be removed or someone cannot escape	unite or bring into contact or bring together the edges of
	cease to operate or cause to cease operating

shut up (adverb)	close up (adverb)
	very close