Adj.: "'I scratch your back, you scratch my back' implies a quid pro quo relationship."
2. An expression which, if used by an insane cannibal psychiatrist you happen to be talking to, is an excellent sign that you're in a LOT of trouble.
2. Lecter: Quid pro quo, Clarisse.
Clarisse (if she'd had ANY sense): Yo, I'm gettin' the hell outta HERE.