A term used when you notice that someone has just crossed the "Point of no return".
"One more shot and he's Done For."
GUY 1: "OMG look at the size of that line he's about to do!"
GUY 2: "He can handle it."
GUY 1: "He's acting really weird now?!"
GUY 2: "He's definatly Done For, let's get the hell outta here, like now."