stoolpigeon vs stool pigeon

stoolpigeon and stool pigeon both are nouns.

Word	Noun	Adjective	Verb	Adverb
stoolpigeon	Yes	No	No	No
stool pigeon	Yes	No	No	No

As nouns, stoolpigeon and stool pigeon are synonyms defined as:

stoolpigeon and stool pigeon: someone acting as an informer or decoy for the police

Other synonyms of stoolpigeon include canary, fink, sneak, sneaker, snitch, snitcher, stoolie.

stoolpigeon (noun)	stool pigeon (noun)
someone acting as an informer or decoy for the police	a dummy pigeon used to decoy others
	someone acting as an informer or decoy for the police