Green’s Dictionary of Slang

an all-day drinking session or any other form of party.

1997		Roger’s Profanisaurus in Viz 87 Dec. n.p.: Leo Sayer rhym. slang All dayer. Bender; prolonged drinking spree; all day party.
2002		D. Shaw ‘Dead Beard’ at www.asstr.org 🌐 Don’t start being cheeky, Dionne. We’ve only just started and I don’t mind making this russel harty a leo sayer.