Green’s Dictionary of Slang

nark n.1

also knark
[Rom. nak, nose]

1. [mid-19C+] a police informer.

2. (UK Und.) a pickpocket’s assistant, who distracts the victim and keeps a look-out.

3. a miser.

4. [mid-19C+] (mainly Aus./N.Z., also narker) an irritating person, a spoilsport, a badly behaved person.

5. [late 19C+] a police officer.

6. [late 19C+] (mainly Aus.) spite, rancour, umbrage; a grudge.

7. [1910s+] any annoying or disagreeable situation.

8. [1920s–30s] (UK tramp) a beggar who works part-time and lives permanently in a common lodging house, thus having a privileged relationship with the owner.

9. [1910s+] one who reports to the authorities, a telltale.

10. [1960s] an agent, a go-between.

11. see narc n. (2)

In phrases

get one’s/the nark (up) (v.)

[20C+] (Aus.) to become angry.

give the nark (v.)

[20C+] (Aus.) of individuals, to anger, to annoy; of objects to ruin to put out of order.

have a nark on (v.)

[1900s] (Aus.) to dislike.