What is the meaning of nark?

noun

• An informer or spy working for the police.
  • synonyms: copper's nark
• A lawman concerned with narcotics violations.
  • synonyms: narc, narcotics agent

verb

• Cause annoyance in; disturb, especially by minor irritations.
  • usage: "Mosquitoes buzzing in my ear really bothers me"; "It irritates me that she never closes the door after she leaves"
  • synonyms: annoy, rag, get to, bother, get at, irritate, rile, nettle, gravel, vex, chafe, devil
• Inform or spy (for the police. ).