polo vs field game

polo and field game both are nouns.

Word	Noun	Adjective	Verb	Adverb
polo	Yes	No	No	No
field game	Yes	No	No	No

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

polo: a game similar to field hockey but played on horseback using long-handled mallets and a wooden ball
field game: an outdoor game played on a field of specified dimensions

polo (noun)	field game (noun)
a game similar to field hockey but played on horseback using long-handled mallets and a wooden ball	an outdoor game played on a field of specified dimensions