split-arse, v. — Green’s Dictionary of Slang

split-arse v.

also split-ass

[SE split + arse n. (1); the movement of one’s legs and buttocks]

1. to move quickly.

1917		‘Omer Drome’ in C.H. Ward-Jackson Airman’s Song Book (1945) 45: So won’t you split-arse back / Along the track / To my dear old Omer Town?
1917		‘My Old Yellow Jacket’ in C.H. Ward-Jackson Airman’s Song Book (1945) 47: He’s returning our fire, / I must split-arse and stunt round him.

2. to act recklessly.

1917

A.S.G. Lee letter in No Parachute (1968) 24 May 18: You can do what you like with your own bus, if you want to loosen it up with show-off splitassing, that’s you own affair.

3. (Aus.) to break wind.

1985

‘Thommo’ Dict. Aus. Swearing & Sex Sayings 123: SPLIT ARSE — to fart.