When you give money to a friend who convinces you that they have a good idea - but they end up totally screwing your over (or fisting you). It turns your investment into an infistment.
Person 1: "Dude, did you invest in Chuck's new business?"
Person 2: "No, man, that is wasn't an investment - it was an infistment"
Person 1: "Infistment?"
Person 2: "Yeah, I haven't felt so taken advantage of since my prostate exam. I will never infist with him again."