Green’s Dictionary of Slang

splash n.2

1. (US short order) soup.

[US]Day Book (Chicago) 8 Sept. 17/1: ‘One order of pea soup,’ a customer will say. ‘Splash of split peas,’ cries the waiter. [...] ‘I want a bowl of tomato soup,’ ordered another, [...] ‘One splash of red noise’.

2. (Aus.) brandy with ice and water.

[Aus](ref. to 1850s) Bulletin (Sydney) 12 Aug. 30/2: In Sydney in the ’fifties [...] a ‘splash’ [was] ice, brandy and water.

3. (UK black/gang) blood.

Loaski ‘Behind Barz’ 🎵 I jugg with the tool, splash don’t fall in a pool.

4. (UK black/gang) a knife.

Harlem Spartans ‘Money & Beef’ 🎵 Spartan step, splash strapped under my tee / Bet I see bare man bleed / [...] / I bet we make bare mums scream.

5. (US) a kill, a corpse.

[US]S.M. Jones August Snow [ebook] A blast from my rifle and his head blossomed crimson. ‘Splash one,’ I heard Frank’s voice say over the walkie-talkie.

In compounds

gang splash (also gang slash)

(Aus.) gang rape of a single female by multiple males, thus v. splash, to engage n multiple sex.

[NZ]Tuohy & Murphy Plum Trees 176: ‘When there was a lot of us and only one girl we’d try and get her to splash for us’ [Simes:DLSS].
[Aus]‘Thommo’ Dict. Aus. Swearing & Sex Sayings 57: GANG SLASH, GANG SPLASH — Where a female is singled out by a group of males for intercourse by all of them.