A word derived from the stoner-culture. It means to act stupid, or do something stupid. It also can mean to be burnt, meaning you are slow or blank, because you're zoned or high.
It is DEFINITELY regional! Me and my crew from DC used it religiously. Once I moved to Miami (and now other parts of Florida) people had NO CLUE what the word was. No one from down here has ever heard of it!
See also:
lunch out (verb or noun),
lunch box (noun), lunch/
lunched (verb)
They said they called me and I missed my turn, but I never left the room! I must have been lunchin or something.
Can someone go get him, we're 15 minutes late already and he's still in his room lunchin!
I can't get through to her at all, man, she's totally
lunchin out over it.
He got arrested last night, the kid drove right into the back of a
parked police car, now THAT is lunchin!!