billiard parlor vs billiard room

billiard parlor and billiard room both are nouns.

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

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

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

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