I. narc 1 /nɑːk $ nɑːrk/ BrE AmE noun [countable] American English informal
[ Date: 1900-2000 ; Origin: narcotic agent ]
a police officer who deals with the problem of illegal drugs
II. narc 2 BrE AmE verb [intransitive + on] American English informal
[ Date: 1800-1900 ; Language: Romany ; Origin: nak 'nose' ]
to secretly tell the police about someone else’s criminal activities, especially activities involving illegal drugs