Sack is derived from the term "sack of shit". It describes someone who is unworthy of
even being filled the feces that would reside within a "sack of shit". It is usually used to describe a person who is extremely
lazy or is performing an extremely
lazy act.
Friend #
1: "Hey man can you shut the lights off?"
Friend #2: "Sorry bro. Busy."
Friend #
1: "
Dude you're right next to them. Just reach over and shut them off."
Friend #2: "Man that's too far away. I'm busy."
Friend #
1: "Busy doing what? You've been playing League of Legends and eating toaster waffles on my couch for six hours."
Friend #2: "Exactly. I'm busy."
Friend #
1: "You're a fucking sack."