So unlikely or surprising as to have been thought impossible; unbelievable.
Vizzini - A Sicilian man of genius. Vizzini is the brains behind the trio (himself, Fezzik and Inigo) were hired by Humperdinck to kidnap and murder Buttercup. He loves the word inconceivable. He is smug, ruthless, and killed quickly in a battle of wits against Westley.