Green’s Dictionary of Slang

gnarly adj.

[SE gnarly; popularized in the film Fast Times at Ridgemont High (1982)]

1. (US campus) bizarre, frightening, amazing.

[US]L.A. Times 21 Sept. IV 16/1: Gnarly: Crazy, like Rad; used for outstanding daring feats or outstanding wipe-outs.
[US]P. Munro Sl. U. 93: gnarly 1. awful, far-out, scary, mind-blowing, hairy.
[UK]Indep. on Sun. Real Life 18 July 5: The situation looks like it might get gnarly.
‘Valley Girls’ on Paranoiafanzine 🌐 I mean, the outfits are pretty gnarly, but you get to fly all over for free, and just think of all the places you could shop! I’m totally gonna be a stewardess.
[US]J. Stahl Pain Killers 94: I don’t know what kinda gnarly shit you were involved in.
[US]T. Swerdlow Straight Dope [ebook] That’s a gnarly tale, dude.

2. (US) a general term of disapproval, disappointment, disgust.

[US]J. Wambaugh Glitter Dome (1982) 289: I wanted my own money and it seemed better than going back to those gnarly massages.
[US]J. Wambaugh Finnegan’s Week 239: Bobbie looked at the dollar bills she’d been given in change and said, ‘Gnarly!’.
[US]S.M. Jones Lives Laid Away [ebook] ‘Remember I had to use a goddamn crate of crowbars to free you from the gnarly talons of the FBI?’.

3. (US campus, also gnarlatious, gnarley, knarly, narly) wonderful, first-rate [on bad = good model].

[US]S. King Stand (1990) 728: How’s that beer? Pretty fuckin gnarly, ain’t it? Hits the spot.
[US]Wash. Post 29 May B3/6: And one recent visitor from Southern California reported that 14-year-olds out there, which is to say the Thought Police of American popular culture, are approving things not as boss, hot, neat, bad, or tough but – are you ready? – ‘gnarly.’.
[US]P. Munro Sl. U. 93: gnarly [...] cool | That girl is gnarly. She goes to every party there is.
[US]Eble Campus Sl. Apr. 5: knarly – cool, neat.
[US]D. Burke Street Talk 2 56: The big mama’s fully macking insanely gnarly grinders. [Ibid.] 60: I’ve never seen such gnarlatious weather!
[US]Eble Campus Sl. Fall 4: gnarley – cool, great: ‘Pulp Fiction was a gnarley movie’.
[US]Da Bomb 🌐 13: Gnarly: 1. Cool. [Ibid.] 20: Narly: Neat, cool.
(con. 1980s) 🌐 gnarly Very good. [...] She is bodacious with gnarly ta-tas.
[US]A. Swartz ‘Sweet, Tight and Hella Stupid’ in S.F. University High School Update Mar.–Apr. 2: gnarley – awesome or cool. ‘A gnarley wave.’.
[Aus]L. Redhead Thrill City [ebook] Tavis may have been able to carve some gnarly pipes, but he was a terrible liar.

4. (US campus) challenging, difficult, intense.

[US]C. Eble (ed.) UNC-CH Campus Sl. 2011.