golf player vs medalist

golf player and medalist both are nouns.

Word	Noun	Adjective	Verb	Adverb
golf player	Yes	No	No	No
medalist	Yes	No	No	No

As nouns, medalist is a hyponym of golf player; that is, medalist is a word with a more specific, narrower meaning than golf player:

Other hyponyms of golf player include driver, golf pro, professional golfer, hacker, hooker, medal winner, medallist, putter, slicer.

golf player (noun)	medalist (noun)
someone who plays the game of golf	(golf) the winner at medal play of a tournament
	someone who has won a medal