"What the fuck were you thinking? What the fuck was I thinking? What the fuck are you doing?; What the fuck is going on? What the fuck just happened? What the fuck is wrong with you?"
2.InterjectionUsed to express astonishment, shock, incredulity, or disbelief (as an ellipsis of longer expressions).
3.InterjectionUsed to express nonchalance or the dismissal of any consequences of something one is about to do.
"I finally said “eh, what the fuck” and quit my job."