nark

A "nark" is a slang word, mostly heard in British and Australian English. Very often, it means someone who tells the police or other people in authority what others have done. In that sense, it points to a sneaky, disloyal person who gives away secrets and gets others into trouble.

The word is strongly negative. It is much harsher than a neutral word like "informant." In Australian English, it can also mean an annoying person or a spoilsport, and as a verb it can mean to annoy someone. You might hear, "Don't be such a nark," when someone is acting like a snitch or spoiling the mood.

"Nark" is an informal word with a sharp edge. In its most common British sense, it means an informer, especially someone who secretly gives the police information about other people. The word does not sound neutral or official. It suggests betrayal, disloyalty, and the breaking of trust inside a group, so calling someone a nark is usually an insult.

In Australian English, the word widened in meaning. It can still refer to an informer, but it can also describe an annoying person, a complainer, or someone who spoils other people's fun. The verb form has similar variety. In British use, "to nark" can mean to annoy someone, as in being "narked" by a rude comment. In some contexts, especially in slang, it can also mean to tell on someone or inform to the police.

The word is commonly linked to the Romany word nak, meaning "nose," which fits the idea of someone poking into other people's business. Whatever its exact path into English slang, it has long carried a rough, street-level tone. You are far more likely to hear it in conversation, crime stories, or informal speech than in careful formal writing. Depending on the place and context, a nark may be a snitch, an irritating person, or someone who simply ruins the mood, but in almost every case the feeling behind the word is clear: strong dislike and distrust.