Green’s Dictionary of Slang

1. (Aus.) a cicada.

[1960		Sydney Morn. Herald 2 Jan. 10/1: The Yellow Monday was a dark brown, and so was his female - that mute, moist cicada with the rude name].
1980		Macquarie Dict. n.p.: pisswhacker [...] a female cicada which makes no sound but squirts a noisome fluid when disturbed .
1987		Sydney Morn. Herald 22 Feb. 38: When I was a boy it was believed that if you caught enough of those cicadas pleasantly known as pisswhackers [etc].
2003		Aus. Word Map 🌐 pisswhacker, a type of cicada that urinated on your hand when you held it.
2012		Renovate Forum 12 Aug. 🌐 What my Dah (and so me as stripling of a lad) called ‘pisswhackers’ ie: cicadas - because if you walk under the trees they are in you will get covered in a fine mist of yellow ‘rain’.

2. (Aus.) something superlative.

1978

H.M. Muheim Vote for Quimby - and Quick! 128: ‘I expect to win. But win or lose, I’m going to have a pisswhacker of a time!’ .

3. (Aus.) of individuals or objects, as a term of abuse.

2003		I Am Faceless 20 Sept. 🌐 I was like wow, you are a stupid pisswhacker.
2010		Bustralia 10 Oct. 🌐 As for the side destos the little pisswhackers Metro has are next to useless, they can hardly be seen.
2013		YourTrackers.net 8 Mar. 🌐 You make the assumption that the people you refer to as ‘pisswhackers’ are youth that still live with their mothers, and have no form of income.

4. (Aus.) something easy.

2003

Atomic Archive 29 May 🌐 Hey man don’t worry, it’ll be a pisswhacker.