Definition:
Nark is a slang term used to describe someone who informs or reports illegal activities to the authorities.
Use case:
You can use the term nark to refer to someone who is seen as a traitor or snitch for reporting illegal activities to the police. For example, "I can't believe he told the cops about our party, what a nark!"
• My little brother is such a nark, he always tells on me when I break the rules.
• The police planted a nark in our group to gather evidence against us.
• I wouldn't trust him, he's a known nark in the criminal underworld.
• He's a nark for always telling our boss when we're not working.
• I don't want to be a nark, but I saw someone cheating on the test.
• Hey, don't be a nark and tell the teacher we were skipping class.