What is Drain The Weasel?
To take a piss (male).
John rises.
Steve: Where you off to? You better not be standing me up for some tidy piece.
John: Nah mate, calm down, this is my 17th pint of Hoffmeister I've got to go and drain the weasel.
See piss, hoffmeister, weasel, pint, tidy piece