short for "crazy ass bitch"; it is a simplified way to call someone such. Can also be short for "crazy ass bitchin'", meaning that either someone is bitching at you or something is totally bitchin' (awesome).
George-Carl: "So, how'd your date go?"
Brendan: "Bro, she was such a cab. She threatened to burn the restaurant down because they gave her regular soda instead of diet."
George-Carl: "Oof, cab to the max."
Sarah: "Check out my new phone!"
Mary: "That's so cab!"