cosplay vs dress up

cosplay and dress up both are verbs.

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

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

cosplay: wear a costume to resemble a character from some media especially anime
dress up: dress in a costume

Other hypernyms of cosplay include costume.

cosplay (verb)	dress up (verb)
wear a costume to resemble a character from some media especially anime	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