Green’s Dictionary of Slang

1. narcotics; also attrib.

1989		(con. 1960s) Courtwright & Des Jarlais Addicts Who Survived 223: At that time they had a ‘narc-vag’ law in Washington. If two or more addicts got together, they could arrest you.
1994		N. McCall Makes Me Wanna Holler (1995) 103: Some MPs with narc dogs walked up.

2. a narcotics agent; also attrib.

1967		N.Y. Times 17 Oct. 44: Most speed freaks get to a point where they’re seeing narks in the trees with cameras.
1969		Time 26 Sept. 41: The culture has its own in-group argot: ‘bummers’ (bad trips) and ‘straights’ (everyone else), ‘heat’ (the police) and ‘narks’ (narcotics agents) and being ‘spaced out’ (in a drug daze).
1970		E. Tidyman Shaft 57: The police didn’t frighten him. The Narcs didn’t frighten him.
1973		E. Bunker No Beast So Fierce 31: He got on the stand and cut Joe loose, but the fuckin’ narks didn’t go for it.
1984		P. Corris ‘Stockyards at Jerilderie’ in Heroin Annie [e-book] Anyone at home in 88? [...] Junkies. [...] You a narc?
1986		C. Hiaasen Tourist Season (1987) 48: I’m beginning to think you’re a narc!
1989		Pileggi & Scorsese Goodfellas [film script] 111: All day I thought the guys in the helicopter were just local cops [...] but they turned out to be Narks.
1998		K. Anderson Night Dogs 51: Dressed in their narc costumes.
1999		Guardian G2 14 July 17: The narcs have been busy busy busy, what with the [...] busts of onetime teen pin-up Leif Garrett and Puerto Rican merengue star Alfred Cotto.
2006		F.X. Toole Pound for Pound 305: He checked the cathedral again for narcs.
2013		T. Dorsey Riptide Ultra-Glide 139: Just in case there’s an undercover narc on the beach.

3. any informer [note nark n.¹ (1)].

1979		H. Feldman et al. Angel Dust 146: He asked me if I wanted to be a narc or an informer or all that bullshit.
1999		Guardian Guide 25 Sept.–1 Oct. 52: He thinks he’s got the narc (‘The rat – it’s fucken Jimmy’).
2006		C. Carr Our Town 258: I thought it likely that people were taking pot-shots at a ‘narc’.
2008		T. Wolff ‘Awaiting Orders’ in Our Story Begins 278: Morse gave nothing away [...] He figured these men for army narcs.

4. in ext. use, any unpleasant person.

1967

H.S. Thompson letter 5 Jan. in Proud Highway (1997) 603: Promoters, narcs, con men – all selling the New Scene to Time magazine.