when your giving it to your lady (in the passion propeller position),when you are just about to ejaculate get up onto your hands and knees and bust onto her stomach and then start rolling around in the cum making pig noises. After collect all the jizz left over and spread it over your ladies ass hole and then lick it all up.
Word coined by Joe Plank of the UK meaning a double sized shot glass filled to the rim, but now generally accepted to mean any larger-than-usual shot of alcohol.