stoolpigeon vs squealer

stoolpigeon and squealer both are nouns.

Word	Noun	Adjective	Verb	Adverb
stoolpigeon	Yes	No	No	No
squealer	Yes	No	No	No

As nouns, squealer is a hypernym of stoolpigeon; that is, squealer is a word with a broader meaning than stoolpigeon:

stoolpigeon: someone acting as an informer or decoy for the police
squealer: one who reveals confidential information to the police or other authority

Other hypernyms of stoolpigeon include betrayer, blabber, informer, rat.

stoolpigeon (noun)	squealer (noun)
someone acting as an informer or decoy for the police	domestic swine
	one who reveals confidential information to the police or other authority