garment vs dress up

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

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

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

garment (noun)	dress up (noun)
an article of clothing

garment (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