A person who is lame. They tend to always flake or be unreliable. They can also sometimes kill the good mood. “Stop being a cab, and let us live a little!” “Don’t trust that guy, he’s a cab”
Imagine hailing a CAB ride in the big apple and that bitch was the Cash Cab. Would you be excited to play for money or pissed those damn bells and sirens scared the shit of you on TV?
My CAB driver was driving so crazily not even Jesus, himself, could have known what to do had he taken hold of the wheel in that moment.