noun, masculine/mu.ʃaʁ/plural: mouchards
(espionage) snitch, grass, tell-tale (police informant); mouchard (undercover investigator); bug (hidden microphone); spyhole, peephole; tachograph (device that records the distance and time traveled by a vehicle)
Synonyms: indic, cafteur, cafard, judas, chronotachygraphe, espiogiciel, logiciel espion, avion-espion
From mouche (“fly”) + -ard (pejorative suffix).