An exclamation used to emphasize surprise, shock, anger, disgust, etc. In this phrase, "in the hell" is used as an intensifier. What in the hell do you think you're doing? You can't come in here!What in the hell? I just had this fixed, and now there's a dent in it!Just what in the hell is going on here?
What (in) the hell?
1. interrog. What has happened?; What? What the hell happened here?
2. interrog. What does it matter? (Usually with the force of an exclamation.) Don’t be such a cheapskate. Get the nice one. What the hell!