nark

verb

To annoy or irritate someone, or to inform on them to authority.

"Don't nark on your mates."

noun

A person who informs authorities, often secretly, about others' wrongdoing.

"He was known as a police nark."

Thesaurus

Synonyms: copper's nark, narc, narcotics agent, get at, devil, get to, chafe, vex, rile, nettle, annoy, gravel