In graffiti terms, to hack is to take either a pen, pencil, or marker and draw a clear line through another's hard work. Why one might choose to hack another's art is usually justified because the artwork was tagged by an opposing artist or personal rival. In some cases, the art just might not appeal to the "hacker" for numerous reasons.
"No reason. It's just that Paul made it; you know how he pisses me off."
2) the shortened term for the game Hacky Sac(much like keep up using a soccer ball) in which you kick a small sac like ball around in a circle consisting of 4 or more people. "They are playing a game of Hack"
see also: Hacky Sac, Biff Master Flex
Amy: I'm down, and I just bought a sick hack the other day too! Just please don't kick me in the face...