Green’s Dictionary of Slang

nark v.1

[nark n.1 ]

1. [mid-19C–1910s] to watch, to survey, to notice.

2. [late 19C+] to inform to the police.

3. [late 19C+] to betray someone; to inform upon.

4. [late 19C+] (mainly Aus./N.Z.) to annoy, to irritate.

5. [1930s+] to complain, to nag.

In compounds

narking dues (n.)

[late 19C] an arrest made on the evidence of an informer.

In phrases

nark the lurk (v.) (also nark the game)

[1930s] (Aus. Und.) to betray a plan.