parlour grand piano vs parlor grand piano

parlour grand piano and parlor grand piano both are nouns.

Word	Noun	Adjective	Verb	Adverb
parlour grand piano	Yes	No	No	No
parlor grand piano	Yes	No	No	No

As nouns, parlour grand piano and parlor grand piano are synonyms defined as:

Other synonyms of parlour grand piano include baby grand, baby grand piano, parlor grand, parlour grand.

parlour grand piano (noun)	parlor grand piano (noun)
a small grand piano	a small grand piano