rounders vs baseball game

rounders and baseball game both are nouns.

Word	Noun	Adjective	Verb	Adverb
rounders	Yes	No	No	No
baseball game	Yes	No	No	No

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

rounders: an English ball game similar to baseball
baseball game: a ball game played with a bat and ball between two teams of nine players; teams take turns at bat trying to score runs

Other hypernyms of rounders include ball, baseball.

rounders (noun)	baseball game (noun)
an English ball game similar to baseball	a ball game played with a bat and ball between two teams of nine players; teams take turns at bat trying to score runs