1) An unspecified act, with the ability to surface in the conversation with vague initialization; a general verb replacement, adding emphasis on the action done.
2) The action/s brought upon in the rare situation of a peg-leg and/or amputee impaling another person’s chest at high velocity, generally in the process of a high-altitude attack.
b. "Oh yeah? Well I duffed your mom last night."
2) (In the context of 'Rules of Engagement')
"Yeah, I can totally see that little stubby girl duffing him in the chest."