Done, okay, finished. In a physical state where further intoxication is unneeded. Often used as a polite refusal for more marijuana, alcohol, etc. Also used as a general term for reluctancy or unwillingness.
"Yo Lee, hit greens on this bowl."
"Aw, no thanks man, I'm champ from that last one."
"Bro, let's throw eggs at some traffic!"
"I'm champ on that, dude. Count me out."