garb vs dress up

garb is a noun but dress up is not a noun.

Word	Noun	Adjective	Verb	Adverb
garb	Yes	No	Yes	No
dress up	No	No	Yes	No

As verbs, dress up is a hyponym of garb; that is, dress up is a word with a more specific, narrower meaning than garb:

garb (noun)	dress up (noun)
clothing of a distinctive style or for a particular occasion

garb (verb)	dress up (verb)
provide with clothes or put clothes on	put on special clothes to appear particularly appealing and attractive
	dress in a costume
	dress in a certain manner
	make something appear superficially attractive
	put a caparison on