stool pigeon vs bait

stool pigeon and bait both are nouns.

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

As nouns, bait is a hypernym of stool pigeon; that is, bait is a word with a broader meaning than stool pigeon:

stool pigeon: a dummy pigeon used to decoy others
bait: something used to lure fish or other animals into danger so they can be trapped or killed

Other hypernyms of stool pigeon include decoy, lure.

stool pigeon (noun)	bait (noun)
a dummy pigeon used to decoy others	something used to lure fish or other animals into danger so they can be trapped or killed
someone acting as an informer or decoy for the police	anything that serves as an enticement

stool pigeon (verb)	bait (verb)
	harass with persistent criticism or carping
	attack with dogs or set dogs upon
	lure, entice, or entrap with bait