To procrastinate or be lazy.
To chill out like fat people.
Beth didn't give the guy a working number because of the stains on his shirt and he looked like a "cabbage".
Manic laughter of crowd around boy #1
Boy #2: "Shit on My boots, You guys are a bunch of cabbages! I'm going to make like Morrison and choke on My own vomit(=leave)."
The victim's bag is taken, emptied, turned inside out, refilled and returned to them, without them knowing anything about it.
Shaun: (looks under chair) Oh for God's sake!
A moment of social ineptitude would also qualify for you to call someone a cabbage.
John; Matt, you fucking cabbage!