a stool pigeon

stool pigeon

An informant, especially a criminal working as a spy for law enforcement officers. Although the criminal agreed to help the police in order to avoid prison time, he was afraid the other gang members would kill him if they discovered he was a stool pigeon.
See also: pigeon, stool
Farlex Dictionary of Idioms.

a stool pigeon

OLD-FASHIONED
A stool pigeon is someone who gives secret information to the police. There's nothing the mob hates more than a stool pigeon. Note: This expression is used to express disapproval. Note: This expression comes from the old practice of putting a wooden pigeon on a seat to trick other pigeons.
See also: pigeon, stool
Collins COBUILD Idioms Dictionary, 3rd ed.
See also:
  • stool pigeon
  • stoolie
  • set a thief to catch a thief
  • throw the book at
  • throw the book at (one)
  • throw the book at somebody
  • throw the book at someone
  • make (one's) bones
  • foul play
  • bust out
References in periodicals archive
She could be an asset to Mano (elder brother) Digong because she would act as a stool pigeon.
Dead men tell no tales
He's also a drugs baron and when she interrupts him in the process of rubbing out a stool pigeon, she has to run for her life.
FILMS OF THE DAY
Police believe the pigeon was meant to represent a stool pigeon - a term for a grass or snitch.
BUTTON YOUR BEAK; EXCLUSIVE Crime bosses' dead bird threat to killer
She told us she couldn't possibly say because she didn't want to be labelled a stool pigeon.
Fanzone: Ask the Prof
What separates a western scrub jay from a stool pigeon? The former knows how to keep its secrets&emdash;especially if it's a jay with a criminal history.
IT TAKES A THIEF
Another television teenager, Meadow Soprano, was lucky: Her dad dropped her off at Bates, Bowdoin, and Colby because he had to track down and murder a stool pigeon. Even if your parents are not similarly occupied, separate anyway during campus visits, and compare notes later.
The Big Choose
A contrasting love stow develops between Boss Whalen's new secretary, Eva (Sherri Parker Lee), and his in-house spy, Canary Jim (Finbar Lynch), who's despised as a stool pigeon by his fellow inmates but who uses his compromised position to break the prison scandal to the world.
Not About Nightingales