stoolpigeon vs informer

stoolpigeon and informer both are nouns.

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

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

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

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

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