Green’s Dictionary of Slang

1. a drunken party; a drunken spree.

1952		K. Amis letter 18 June in Leader (2000) 286: A piss-up, travelling expenses, and five bob?
1966		T. Keyes All Night Stand 49: Ben did not want to have a piss-up in a hotel later.
1967		J. Wynnum I’m a Jack, All Right 119: As far as the fellers are concerned any excuse for a P.U. is good one.
1973		B.S. Johnson All Bull 34: Hardbitten ready-for-anything faces that were more than a little ready for the giant piss-up that would mark the end of our basic training.
1974		Tharunka (Sydney) 8 May 5/1: At the Palace, Groover Gough attending one of the regular Canberra piss-ons in Kings Hall, was heard to remark to Frank Dream over a schooner of ‘Workers Milk’ that everything was go ahead for the coming elections.
1985		B. Humphries Traveller’s Tool 21: Even at ultra-sophisticated piss-ups like State Premiers’ receptions.
1998		P. McCabe Breakfast on Pluto 98: The soldiers are aht and abaht, having themselves a good old piss-up like!
1998		R.G. Barrett Mud Crab Boogie (2013) [ebook] [Y]ou would have thought they’d just come back from a giant piss-up instead of a training session.
1999		Guardian G2 29 July 14: Travellers warm up for a piss-up in the sun with six hours in the bar.
2000		Indep. Rev. 24 Mar. 9: Three couples bicker and snipe at one another at their ‘piss-up dinner’.
2000		S. Maloney Big Ask 286: Not pleased to have been summoned from some Friday-night piss-up.
2007		D. McDonald Luck in the Greater West (2008) 128: There were five or six Aussies having a piss-up at one of the barbecue tables.
2011		Guardian 9 Apr. 18/1: The grandiosely named Conference on World Affairs which [...] is basically a piss-up with speeches.
2015		Indep. on Sunday 25 Oct. 🌐 He knew that the hedonism had gone too far when he found himself attending a piss-up celebrating Action Man.

2. attrib. use of sense 1.

1993

S. McAughtry Touch and Go 5: Johnny had saved my bacon a good few times on the HQ campus after piss-up balls-ups.