Green’s Dictionary of Slang

1. (orig. milit.) to remove, to cancel, to dismiss (e.g. from a course).

1921		N&Q 12 Ser. IX 348: Wash Out (To). To cancel, suppress.
1929		(con. 1916) F. Manning Her Privates We (1986) 200: This overcoat business will have to be washed out.
1934		Wodehouse Right Ho, Jeeves 224: Why not chuck the whole idea of hitching up with me? Wash it out altogether.
1949		I. Shulman Cry Tough! 94: His mother and father didn’t understand him [...] And now – Larry and Bull – had washed him out.
1958		E. Gilbert Vice Trap 51: I’d been in basic training [...] and I was through the next week, washed out.
1961		‘Frank Richards’ Billy Bunter at Butlins 10: Too late to wash it out now, isn’t it, Greeney?

2. (US) to lose all one’s money, esp. from gambling.

1931

D. Runyon ‘The Snatching of Bookie Bob’ in Runyon on Broadway (1954) 121: We are washed out. We owe every bookmaker at the track.

3. to lose or spoil anything.

1935		E.W. Calder ‘Black 13’ in Spicy Adventure Stories Aug. 🌐 You were a pilot on the Trans-American Air Lines. You washed out your ship over the desert.
1941		C.R. Bond 31 Dec. in A Flying Tiger’s Diary (1984) 69: He is okay but washed out his landing gear.

4. (US) to die, to be killed.

1937

E.C. Parsons Great Adventure 183: He was in a bad spot to defend himself [but] he had ideas that were decidedly averse to getting washed out .

5. to fail, e.g. a course.

1943		M. Curtiss Letters Home (1944) 10 May 5: Such a great number ‘wash-out’ (fail) that I wouldn’t want anyone to know if I failed the course.
1953		L. Uris Battle Cry (1964) 49: There’s a kid [...] who wants to make Sea School but he washes out.
1968		‘Hy Lit’ Hy Lit’s Unbelievable Dict. of Hip Words 44: wash out – Fail completely.
1993		B. Moore Lex. of Cadet Lang. 420: usage: ‘He washed out in Chem.’.
2003		J. Ellroy ‘Stephanie’ in Destination: Morgue! (2004) 59: They checked out the Standard Club [...] The Standard Club washed out.
2012		L. Berney Whiplash River [ebook] ‘I probably should have washed out at Quantico. My first SAC actually told me that straight up’.

6. (US) vtr. to kill, to assassinate.

1967

R. Starnes Requiem in Utopia 70: There must have been a dozen opportunities to wash him out before he left London. Why wasn’t it done?