Green’s Dictionary of Slang

1. (Aus.) thrown from one’s horse.

1903		Sydney Stock and Station Jrnl 17 Apr. 12/4: There are diversities of poets and liars, many ways of getting ‘slung’ from a buck-jumper, but only one way of making love.
1937		Queenslander (Brisbane) 2 Sept. 33/2: It all happened from the day Jim Penrose got slung by ‘Snakey’ and broke his neck.
1941		Baker Popular Dict. Aus. Sl.

2. acquitted.

1989

J. Morton Lowspeak 130: Slung – to be acquitted.