A police spy or informer.

slang. A spy or informer, esp. for the police.

Esp. in France or French-speaking regions: an undercover agent or investigator, a police spy.

slang. A person who gives information, esp. of an incriminating nature, on another person to the police or other authority, an informer; spec. an…

(a) U.S. a pigeon fastened to a stool as a decoy; chiefly figurative of a person employed, especially by gamblers, as a decoy; (b) a police informer.

A hard-hearted, unfeeling person.

a person who gives information to the police about crimes and their perpetrators, esp. one who does this on a regular basis.

An informer; spec. (more fully copper's nark) a police informer. Cf. nose, n. 4.

slang. Australian. A person who alerts a bushranger to the movements of potential threats, esp. the police. Cf. bush telegraph n. at bush, n.1…

A policeman; also attributive, as in copperstick, a policeman's truncheon. Hence, one who informs on fellow prisoners; a police informant; esp. to co…

In Birmingham: a police informer. Also as v. intransitive = inform, v. 4b.

slang. = nark, n. 1a 2a.

U.S. A police informer. Cf. stool-pigeon n. at compounds 2.

slang. A police informer.

Originally and chiefly Criminals' slang (chiefly North American). An informer; esp. a person who gives information to the police about an offence…

slang. A police informer. Now rare.

A police informer, a stool-pigeon.

A police informer. Australian slang.

British slang (originally Criminals' slang). A police informer. Later also more widely: any person who informs on another. Cf. grasshopper, n. 11b g…

British slang (chiefly Criminals' slang). Now somewhat rare. A police informer. Cf. grass, n.1 12a, grasser, n.2

A police informer; (later also more widely) any person who informs on another; = grass, n.1 12a. Cf. grass, v. 9.

In Russia: an informer; a ‘stool pigeon’.

A police informer who informs on a large number of individuals or whose information is of exceptional value.