Drinking to the point where you lose the ability to record memories, also known as getting "blacked out." The amount of alcohol necessary to achieve this state varies from person to person. This is often when you do the stupidest shit you've ever done, common examples are: sexing a fatty, pissing/shitting/yacking in unacceptable places (anywhere but a bathroom), and looking/acting fucking retarded. Luckily you won't remember it, hopefully your friends will.
Friend 1: Dude when I got back from the bars last night you were posted in the front lawn, wacking it with the sprinklers on