derivative of 'cabinet', as in liquor cabinet. "Checking the cab" refers to seeing what alcohol is available for consumption.
'Yo, Imma raid the cab...'
'But you're the designated driver...?'
(adj/state of mind) Lost, usually used to mean that one doesn't know what the hell's going on.
Dude, did you and Kelly get into a fight or something? I am SO Columbus on this whole sitch