A shortened form of “what the fuck are you saying right now?” Used as an expression of disbelief of how absolutely retarded an individual can be. Usually said in an unnaturally high voice.
When a dumb or similarly challengedin the brain person has done something that makes you say dafuq? Whatever has caused the exclamation of dafuq is the act of dafuquery. Something that's just not right. What in the actual fk? That's dafuquery.