Green’s Dictionary of Slang

1. (orig. US) unpleasant, emotional, rude, tactless, unsophisticated, unfair; various negative meanings as to a particular context; thus n. uncoolness, the state of lacking such neg. qualities.

1953		‘William Lee’ Junkie (1966) 61: It’s better to meet alone like this [...] Nick is a very un-cool guy.
1961		T. Taylor Baron’s Court All Change (2011) 124: [This] is without doubt the uncoolest thing that anyone could do.
1967		J. Horton ‘Time and cool people’ in Trans-action 4 8/2: Survival requires that a hustling dude know who is cool and uncool (who can be trusted).
1969		D. Di Prima Memoirs of a Beatnik 147: [A]fter a while it got spooky. Billy Daniels got shot [...] We decided it was getting uncool [. . .] so we split and went home.
1969		Gandalf’s Garden 6 n.d. 11: uncool: reckless, jittery, loudmouthed, paranoid, or causing a situation where consequences would be unfavourable.
1979		Lette & Carey Puberty Blues 1: The bad surfboard riders [...] the Italian family groups and the ‘uncool’ kids from Bankstown.
1989		T. Wolff This Boy’s Life 43: But it wasn’t really our looks that made us uncool. Coolness did not demand anything as obvious as that. Like chess or music, coolness claimed its own out of some mysterious impulse of recognition. We had been claimed by uncoolness.
1993		I. Welsh Trainspotting 283: Begbie’s so fuckin uncool man.
1997		(con. 1970s) G. Pelecanos King Suckerman (1998) 220: Stay away from those knuckleheads be tellin’ you it’s uncool to learn.
2002		Fabian & Byrne Out of Time (ms.) 73: She seemed determined to do all the uncool things in her uncool situation.
2012		D. O’Donnell Locked Ward (2013) 147: That’s what uncool dudes can’t fathom. You know? Like religious zeroes.
2022		J. Hannaham Didn’t Nobody Give a Shit 162: She behaving uncool in ezzackly the way Ise tryna behave cool.

2. (US) constr. with the, something unappealing.

2016

The Cut (NY Times Mag.) Mar. 🌐 The Uncool (or in Chloe’s words, The Lame, The Yikes).