mental, adj. — Green’s Dictionary of Slang

mental adj.

1. insane, crazy, out of one’s mind.

1897		A.H. Lewis Wolfville 115: Texas is still in a fog, speakin’ mental, an’ about bled to death; while them exhortin’ people is outen their minds entire.
1936		W. Holtby South Riding (1988) 62: The mother’s in an asylum and the child’s mental as anything.
1941		G. Kersh They Die with Their Boots Clean 78: Gord forgive him. He’s mental.
1959		A. Sillitoe ‘The Match’ Loneliness of the Long-Distance Runner (1960) 119: You’re a lunatic [...] You’re mental.
1962		F. Norman Guntz 65: It’s enough to drive you mental.
1973		(con. mid-1960s) J. Patrick Glasgow Gang Observed 79: Wee Frankie, pure mental he is, brass-necked it, walkin’ up the road wi’ his stupid, mid-grey flannels.
1975		S. Roberts ‘For No Reason’ Outside Life’s Feast 58: I’m sure that kitchen kaffir is mental.
1981		W. Russell Educating Rita I i: rita: Do you understand that? frank: Yes. rita: Yeh. They wouldn’t round our way. They’d think I was mental.
1998		I. Welsh Filth 89: The Beast is fuckin mental.
2000		N. Griffiths Grits 231: Spent some time in Northern Ireland, before the ceasefire like ... that must be enough t’send anybody fuckin mental.
2006		P. Shannon Davey Darling 26: Some people would consider them mental [...] not quite right in the head.
2009		L. McIlvanney All the Colours 84: ‘You’re mental, Diane’.
2012		(con. 1980s) I. Welsh Skagboys 15: The bastards charge forward and it’s fucking mental.
2012		A. Wrangles ‘A Forgiving Kind of Nature’ in Crime Factory: Hard Labour [ebook] They think you’re mental, Mum. Crazy.
2015		I. Welsh Decent Ride 125: Ah liked that lassie. Rough as fuck and a wee bit mental, but she was sound.
2018		C. Hammer Scrublands [ebook] ‘He went mental and shot everyone’.
2020		G. Armstrong Young Team 5: ‘[T]he cunt is fuckin mental [...] actually off his nut’.

2. a general intensifier meaning wonderful, bizarre, terrifying, according to context.

1994		I. Welsh ‘A Smart Cunt’ in Acid House 277: This acid is mental shit . . . Spud says.
1998		A. Warner Sopranos 116: Hot shite. Fucking mental.
2000		Guardian Guide 1–6 Jan. 18: Big up to everyone who went clubbing on NYEY2K and made it such a mental booyaka ding dong.
2012		J. Fagan Panopticon (2013) 158: The big shoes he’s chored look mental.
2017		L. McInerney Blood Miracles 49: ‘What’s it like down there?’ Ryan looks behind at the open door. ‘Fairly mental, like’.
2019		P. Baker Fabulosa 294/2: mental the best! (or the worst!).

3. angry.

2000		N. Barlay Crumple Zone 135: If Dad finds out about the stealing [...] he gets more mental than with surfing.
2012		(con. 1980s) I. Welsh Skagboys 146: He disnae look mental now, jist a scared laddie.

In derivatives

mentalled (adj.)

(UK teen) intoxicated by drink or drugs.

2007

Skins ser.1 ep.3 [TV script] She is drunk [...] totally mentalled.

In phrases

go mental (v.)

1. to become insane, to have a mental breakdown or outburst.

1967–8		Baker et al. CUSS 156: Go mental Go wild.
1978		R. Price Ladies’ Man (1985) 175: Whata you goin’ mental on me, Kenny?
1981		Eble Campus Sl. Mar. 3: go mental – become increasingly mentally unstable.
1991		F. Mac Anna Last of the High Kings 101: The dog’s gone mental. [Ibid.] 104: The chicks will go mental for us.
2001		N. Barlay Hooky Gear 6: Monica is gonna go mental when I take hers for the school run in the a.m.
2017		A. Parks Bloody January 4: No wonder the papers were going mental.
2020		A. Parks Bobby March Will Live Forever 70: ‘Jumbo forgot [to remove his shoes] one day and she went fucking mental’.

2. to have an uproarious time.

2000

Guardian Guide 8–14 Jan. 26: The whole place is going mental to that wicked William Orbit tune.

SE in slang uses

In compounds

mental giant (n.)

(US campus) a fool, an idiot.

1989

P. Munro Sl. U.

mental hernia (n.) (US)

1. a fool, an idiot.

1971

E.E. Landy Underground Dict. (1972) 130: mental hernia n. Seemingly ignorant person.

2. a mental breakdown.

1972

B. Hannah Geronimo Rex 26: The old man fell into his study for about two weeks of fake mental hernia [...] and hollered at anybody who disturbed him.

mental job (n.) [job n.² (4)]

one who is or potentially might be insane.

2002

geolinda ‘Superhawk’ on RunLevelZero 🌐 I’ve been cursing out loud like a mental job for the last hr.

mental midget (n.)

(US) a stupid person.

1966		oral testimony in Lighter HDAS II.
1989		P. Munro Sl. U.
2004		J. Gorman My Last Busy Season 364: I would leave right now if I weren’t leaving this place in the hands of a crook and your son, the mental midget.