Green’s Dictionary of Slang

wash v.

1. to adulterate liquor with water.

[Ind]H. Hartigan Stray Leaves (2nd ser.) 7: [T]he canteen sergeant supplied him with as much liquor as he could pay for after it was well washed, and the harm taken out of it,.

2. (US Und.) to kill, to murder, to assassinate [fig. use of SE wash out].

[US]Z.N. Hurston Jonah’s Gourd Vine (1995) 4: Hit me if you dare! Ah’ll wash yo’ tub uh ’gator guts and dat quick.
[US]E. Torres Carlito’s Way 32: If push comes to shove, we can wash him.
[US]E. Little Another Day in Paradise 137: I’ve got to slow down my using and drinking or I’ll get washed.
[US]Wiley ‘Grew Up In’ 🎵 Where the olders are washed and the young Gs out on the blocky want grief.

3. to ‘de-criminalize’ corruptly or illegally gained money by ‘washing’ it through a casino till or bank; thus wash-up, the act of ‘laundering’ money; washing machine, a place, e.g. a nightclub, used for this purpose[var. launder v.].

Black Panther 30 June 2/2: The money had been ‘washed’ through the Mexican bank passing off as a legal fee to the Mexican lawyer in order to conceal the source of the donation.
[US]T. Philbin Under Cover 45: John Castelli was washing the money for them. Perhaps he tried to rip them off.
[Aus]R.G. Barrett Between the Devlin 126: [L]ike most crime figures, [they] didn’t mind getting into a bit of heavy gambling to wash away a bit of black money.
[Aus]R.G. Barrett Leaving Bondi (2013) [ebook] [T]here was still an attractive tax break for investing in a meat-pie western, so he wouldn’t lose that much in the wash-up .
[Aus]R.G. Barrett Leaving Bondi (2013) [ebook] In five minutes Les had his money, and all nicely washed through a bookie so it looked like Les had won it at the races.
Sun. Herald 16 Mar. 🌐 One money-laundering racket was exposed when an employee of a casino offered to wash money for a gangster who turned out to be an undercover police officer.
[US]Simon & Burns ‘Straight and True’ Wire ser. 3 ep. 5 [TV script] Ain’t got your little spot for you to wash that dirty money.
[US]T. Pluck Bad Boy Boogie [ebook] ‘The club’s a washing machine for Frankie Dellamorte’s money’.
[US]D. Winslow ‘Crime 101’ in Broken 72: He fences the rocks, washes the proceeds.
[Ire]L. McInerney Rules of Revelation 341: ‘[W]e invested wisely. It was washed clean and our fee pumped into Catalyst and a few other businesses’.

4. (drugs) to alter the properties of cocaine base by a chemical process.

[UK] in R. Graef Living Dangerously 97: We washed out a gram of it and had a bit.
[UK]N. Barlay Crumple Zone 33: The guys are discussing the joys of household ammonia and the best way to wash rocks.

In compounds

wash-house (n.)

a business used as an ostensibly legal ‘front’ for laundering illegally gained money.

[UK]K. Sampson Killing Pool 71: We’ll be running a wire on the travel agency, too. Even preliminary checks show it’s likely being used as a major, major wash-house.

In phrases

wash away (v.) (US)

in fig. use, to overwhelm.

[US]Mezzrow & Wolfe Really the Blues 249: We felt too good to be upset by a puny police raid. It almost washed us away.

SE in slang uses

In compounds

wash and go [play on the brandname shampoo]

(gay) a phr. describing the act of leaving immediately after sex; also as adj.

BCN Bi Issue 10, Aug. 🌐 In the same week, ‘HIV Life’ (the HIV issues section of The Pink) told of The HIV Project’s (I think they mean the SIGMA Project) report on behavioural bisexuals. It got... one column inch focusing on the fact that one respondent described his encounters with men as ‘Wash and go sex.’.
wash-belly (n.) [the image of finally ‘cleaning out’ the womb]

(W.I.) a woman’s last child.

[UK]N. Farki Countryman Karl Black 5: Although Miss Birdie loved all her children, she had a tender spot in her heart for the ‘wash-belly.’.
wash-mouth (n.)

liquor.

Memoirs of the Late Capt. Hugh Crow 45: Massa Crow [...] me want you for give me some was’ mouth [...]I knew that ‘wash mouth’ meant a dram.
washtub (n.)

(US) a boat.

[US](con. WWII) T. Sanchez Hollywoodland (1981) 72: Buddy, you wouldn’t catch me on no washtub out there in the drink.

In phrases

wash one’s brain (v.) (also wash one’s head)

to drink wine.

[UK]Partridge DSUE (8th edn) 1309/2: Wash one’s brain, head, etc. to drink wine.
wash one’s foot in the tank (v.)

see under tank n.1

wash one’s ivories (v.)

see under ivory n.

wash one’s milk off one’s liver (v.) [the idea that milk rather than blood is running through one’s veins]

to stop behaving in a cowardly manner.

[UK]R. Cotgrave Dict. of Fr. and Eng. Tongues n.p.: Souhait, Wash thy milke off thy liuer (say we).
wash one’s mouth (out) (v.)

to have a drink.

[UK]Sporting Times 29 Mar. 1/4: Here, boys [...] come on down to the other bar and wash your mouths out.
[UK](con. c.1910) J.B. Booth London Town 304: Like to wash yer mouth? I’ve touched lucky the last couple o’ days.
wash one’s mouth upon (v.)

(W.I.) to gossip about, to denigrate behind someone’s back.

[WI]L. Bennett ‘Scrape Thru’ in Jamaica Dialect Verses 19: Dah ’oman Miss Matty gwine look shame yuh se’ / Meck she gwan wash har mout’ ’pon Nelly / For ole ’oman dah swear fe nyam peppa-pot / It dah swear fe hat har belly.
[WI]L. Goodison Baby Mother and King of Swords 15: Old nyaga was washing them mouth pan me more than ever.
wash out

see separate entries.

wash up

see separate entries.