Just launched! Learn slang while watching funny vids: urbandictionary.tv
1. stacks on
A game where one person is 'it', and someone yells "Stacks ON!" and everyone playing tackles or jumps onto that person.

Word of warning, it is very easy to injure yourself, or other people playing :)
Person one: Im bored. I'm going for a walk
Person two: STACKS ON!!!!!!
Person one: Oh no..