Green’s Dictionary of Slang

lose it v.

1. to lose control temporarily; in an extreme case to have an actual mental breakdown, to go mad.

[[UK]Story of a Lancashire Thief 9: He had been a jigger-dubber [...] but got sacked for boozing, and then he lost himself. [Ibid.] 15: (lost himself) Went lower and lower].
[[US](con. 1920s) J.T. Farrell Young Manhood in Studs Lonigan (1936) 208: Hey, grandpa! Button up. You’re losing something].
[[UK]H. Brown Walk in Sun 102: They had their morale back. Not that they had ever really lost it. They had simply been a little uncertain of themselves].
[US]C. Himes If He Hollers 155: [H]e wanted to kill me because I had seen him lose it.
[US]E. De Roo Go, Man, Go! 23: He signalled to Gil not to say anymore. Gil lost it.
[US]H.S. Thompson Hell’s Angels (1967) 98: The minute you hit the brakes you’ll start losing it; bikes don’t drift like cars.
[US]Eble Campus Sl. Apr. 3: lose it – unable to cope, astounded, rattled.
[US](con. 1969–70) D. Bodey F.N.G. (1988) 37: The last guy who rotated out [...] was out here in the Bush for three hundred and fifty days. [...] he was fuckin’ losing it the last couple weeks.
[UK]K. Lette Llama Parlour 80: Look, if ya think you’re gonna lose it and say somethin’ totally stoo-pid, well, I dunno.
[Ire]P. Howard Curious Incident of the Dog in the Nightdress 27: I end up totally losing it [...] and we’re talking totally.
[SA]IOL News 5 Dec. 🌐 I am a very prim and proper person [...] my clients se me as the business type. It should be interesting how it is going to look when they see me lose it.
M. MacLean ‘Just Like Maria’ in ThugLit Oct. [ebook] ‘Miguel loses it [...] He breaks a bottle and...’.
[UK]Guardian G2 3 July 5/1: Did I lose it, am I crazy, man?
[Ire]L. McInerney Glorious Heresies 163: She was [...] in the process of completely losing it right there on his couch.
[US]Rayman & Blau Riker’s 110: [O]ne night he just sort of lost it and acknowledged the first time that he was feeling very depressed.

2. to lose one’s virginity.

[Aus]R.S. Close With Hooves of Brass 40: Never since she had first lost it, had she experienced such a drought.
[UK]Sun. Times Mag. 30 Sept. 34: ‘How old were you when you lost it?’ ‘Fifteen years eleven months and two weeks.’.

3. (US campus) to be surprised, to be shocked.

[US] P. Munro Sl. U.

4. (US campus) to vomit.

[US]Eble Campus Sl. Oct.
[UK]M. Belmonte Compter Science and Why (1993) 🌐 I was struck with [...] the plethora of words and phrases meaning ‘vomit’ and/or ‘to vomit’ [...] At most American colleges and universities, a weekend cannot pass without seeing multitudes [...] lose it.

5. to lose one’s skills, abilities.

[UK]J. Mowry Way Past Cool 131: You losin it, man . . . lettin some little sucker slice you like that.
[US]W.D. Myers Handbook for Boys 13: Moms thinks maybe [my uncle’s] losing it in the mental department.

6. to pass out.

[UK]K. Richards Life 489: I remember a show in Italy where I really knew I was losing it [...] The air was totally dead and I started to feel myself going.