stool pigeon
noun
1
: a person acting as a decoy or informer
especially : a spy sent into a group to report (as to the police) on its activities
2
: a pigeon used as a decoy to draw others within a net
Synonyms
- betrayer
- canary [slang]
- deep throat
- fink
- informant
- informer
- nark [British]
- rat
- rat fink
- snitch
- snitcher
- squealer
- stoolie
- talebearer
- tattler
- tattletale
- telltale
- whistle-blower
See all Synonyms & Antonyms 
Example Sentences
the FBI finally got a break when one of the mob boss's top henchmen turned stool pigeon
Recent Examples on the Web They are barred from using certain language during debates including git, guttersnipe, swine and stool pigeon. 
Max Colchester, WSJ, 3 Jan. 2019
Max Colchester, WSJ, 3 Jan. 2019 Word History
Etymology
probably from the early practice of fastening the decoy bird to a stool
First Known Use
1826, in the meaning defined at sense 1
stool pigeons
noun
as in informants
a person who provides information about another's wrongdoing the FBI finally got a break when one of the mob boss's top henchmen turned stool pigeon Synonyms & Similar Words
Relevance
- informants
- informers
- deep throats
- canaries
- snitchers
- stoolies
- rat finks
- rats
- collaborators
- talebearers
- spies
- squealers
- tattlers
- snitches
- tattletales
- betrayers
- narks
- finks
- telltales
- whistle-blowers
- gossips
- gossipers
- blabbermouths
- snoops
- leakers
- blabbers
- snoopers
- notifiers
- under a spell
- under a/the microscope
- under an alias
- under appeal
- under arrest
- under assault
- under attack
- under bevel
- under budget
- under canvas
- under certain circumstances
- under compulsion
- under consideration
- under construction
- under contract
- under control
- under cover
- under cover of anonymity
- under cover of darkness
- under cover of night
- under deadline
- under debate
- under discussion
- under discussion/consideration/review
- under examination