A game much beloved of students whereby the ultimate purpose is to end up in bed with a total stranger. As you do. Basically you turn up to the pub and get given a number (all blokes have even numbers and all girls have odds or vice versa). From this relative safety of anonymity you can leave a message up on a board, something of profound intellectual significance like "Number 31 you are really fit" or "fancy a shag Number 25?" Hopefully there will be so much booze going round that sex is inevitable, and you're guaranteed to wake up in the morning feeling slightly disgusted with yourself and quite possibly an STD. Great fun.
I went to that shag tag last night, ended up with the clap.