canteen vs rec room

canteen and rec room both are nouns.

Word	Noun	Adjective	Verb	Adverb
canteen	Yes	No	No	No
rec room	Yes	No	No	No

As nouns, rec room is a hypernym of canteen; that is, rec room is a word with a broader meaning than canteen:

Other hypernyms of canteen include recreation room.

canteen (noun)	rec room (noun)
a flask for carrying water; used by soldiers or travelers	a room equipped for informal entertaining
restaurant in a factory; where workers can eat
a recreation room in an institution
a restaurant outside; often for soldiers or policemen
sells food and personal items to personnel at an institution or school or camp etc.