close down vs close up

close down and close up both are verbs.

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

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

Other synonyms of close down include close, fold, shut down.

close down (verb)	close up (verb)
cease to operate or cause to cease operating	refuse to talk or stop talking; fall silent
	block passage through
	unite or bring into contact or bring together the edges of
	cease to operate or cause to cease operating

close down (adverb)	close up (adverb)
	very close