Wiktionary
n. (context UK Australia New Zealand vulgar slang English) A party where people consume alcohol.
WordNet
n. vulgar expression for a bout of heavy drinking
Usage examples of "piss-up".
Gar told us that under interrogation the narcos had revealed that after a big farewell piss-up the day before the attack, some of their number had left the camp to escort the other two Europeans down river.
Royal Navy called this place HMS Peafowl, the sailors called it HMS Piss-up.
We could be sitting there in the daytime in our FRP, ready to do a first-light attack, and six boatloads of narcoguerrillas could slip quietly into the camp for a big piss-up.
We could be sitting there in the daytime in our FRP, ready to do a first-light attack, and six boatloads of narcoguerrillas could slip quietly into the camp for a big piss-up.