Duffed (v) - The act of getting used and or manipulated by an attractive, mentally unstable person of the opposite sex. Unfortunately this includes an abundance of flirting, profound mixed messages, and sexual enuendos that don't actually lead to SEX, merely the illusion that it will. The Duff usually ends by the Duff-er getting back together with their original girl/boyfriend, leaving the duff-ee with a killer case of blue balls/dry-gina.
Verb: to Derf is to purposfully send someone the wrong way, or to trick someone into going the wrong way. You have to strike it with such confidence and not to stutter that they do not second guess you and still believe they are going the right way. Even when they know they have gone the wrong way, they blame or doubt themselves.