slang for police informer
1 noun a paid police informer. â 2 Noseâ was used to denote a police spy or informer and so were slang synonyms such as nark, snitch and snout. 3  Snout is of more recent origin than the other terms, dating from between the world wars. 4  noun tobacco, a cigarette.
The term presumably derives from the informant 'sniffing out villains'. Other slang terms for a police informant include grass, stool-pigeon and copper's nark. Getting snout in jail is a nightmare if you used to be a police snout.