water polo vs athletic game

water polo and athletic game both are nouns.

Word	Noun	Adjective	Verb	Adverb
water polo	Yes	No	No	No
athletic game	Yes	No	No	No

As nouns, athletic game is a hypernym of water polo; that is, athletic game is a word with a broader meaning than water polo:

water polo: a game played in a swimming pool by two teams of swimmers who try to throw an inflated ball into the opponents' goal
athletic game: a game involving athletic activity

water polo (noun)	athletic game (noun)
a game played in a swimming pool by two teams of swimmers who try to throw an inflated ball into the opponents' goal	a game involving athletic activity