winner vs prize winner

winner and prize winner both are nouns.

Word	Noun	Adjective	Verb	Adverb
winner	Yes	No	No	No
prize winner	Yes	No	No	No

As nouns, prize winner is a hyponym of winner; that is, prize winner is a word with a more specific, narrower meaning than winner:

Other hyponyms of winner include lottery winner.

winner (noun)	prize winner (noun)
the contestant who wins the contest	the winner of a lottery
a gambler who wins a bet
a person with a record of successes