dress up vs garb

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

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

As verbs, garb is a hypernym of dress up; that is, garb is a word with a broader meaning than dress up:

Other hypernyms of dress up include apparel, clothe, dress, enclothe, fit out, garment, habilitate, raiment, tog.

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

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