cosplayer vs player

cosplayer and player both are nouns.

Word	Noun	Adjective	Verb	Adverb
cosplayer	Yes	No	No	No
player	Yes	No	No	No

As nouns, player is a hypernym of cosplayer; that is, player is a word with a broader meaning than cosplayer:

Other hypernyms of cosplayer include participant.

cosplayer (noun)	player (noun)
Someone who wears a costume from a comic book or similar media	a theatrical performer
	a person who participates in or is skilled at some game
	someone who plays a music as a profession
	a person who pursues a number of different social and sexual partners simultaneously
	someone who takes part in an activity