There are 2 results of your search for donk2.
donk1
to give a lift on your bicycle (similar to dink): Hop on my bike and I'll give you a donk.
Contributor's comments: Used in SE Vic, diminutive form of donkey. So ... "He's a real donk, that bloke..."
Contributor's comments: While I was at high school in Canberra as recently as two years ago, the term 'dink' was used instead of 'donk'.
donk2
1. a motor: His new car has a big donk.
2. the membrum virile.
Contributor's comments: Donk normally refers to a car engine in Perth although I can remember it also referring to the male anatomy when I was a kid.
Contributor's comments: I grew up in SE Queensland and the term we used was "dink". A donk referred to a car engine or part of a male's anatomy.
Editor's comments: These two meanings of "donk" are general Australian slang and not regionalisms. "Donk" in the sense of "a dink on one's bicycle", on the other hand, is a regionalism. See "donk 1".