attire vs dress up

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

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

As verbs, attire and dress up are synonyms defined as:

attire and dress up: put on special clothes to appear particularly appealing and attractive

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

attire (verb)	dress up (verb)
put on special clothes to appear particularly appealing and attractive	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