Green’s Dictionary of Slang

piss-up n.

also piss-on, p.u.
[pissed adj.1 ]

1. a drunken party; a drunken spree.

[UK]K. Amis letter 18 June in Leader (2000) 286: A piss-up, travelling expenses, and five bob?
[UK]T. Keyes All Night Stand 49: Ben did not want to have a piss-up in a hotel later.
[Aus]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.
[UK]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.
[Aus]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.
[Aus]B. Humphries Traveller’s Tool 21: Even at ultra-sophisticated piss-ups like State Premiers’ receptions.
[Ire]P. McCabe Breakfast on Pluto 98: The soldiers are aht and abaht, having themselves a good old piss-up like!
[Aus]S. Maloney Big Ask 286: Not pleased to have been summoned from some Friday-night piss-up.
[Aus]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.
[UK]Guardian 9 Apr. 18/1: The grandiosely named Conference on World Affairs which [...] is basically a piss-up with speeches.
[UK]Indep. on Sunday 25 Oct. [Internet] 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.

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