An abbreviation of the phrase "What the fuck?". Commonly used at social events to express shock or awe.
A friend staples his nipples to his dick hole, covers his butt cheeks in peanut butter and asks you to clean him out before the chess master comes back. Dafuh?
DaFuh (Duh-Fuh) Is something you say when something was so random, stupid, or insane that it's hard to comprehend what you just saw or heard. It is used the same way as What the Fuck and What the Hell, but a bit more extreme, and when you're kind of confused.
DaFuh...? What the fuck did I just watch!?