billiard room vs billiard saloon

billiard room and billiard saloon both are nouns.

Word	Noun	Adjective	Verb	Adverb
billiard room	Yes	No	No	No
billiard saloon	Yes	No	No	No

As nouns, billiard room and billiard saloon are synonyms defined as:

Other synonyms of billiard room include billiard hall, billiard parlor, billiard parlour.

billiard room (noun)	billiard saloon (noun)
a room in which billiards is played	a room in which billiards is played