what on earth

An exclamation used to emphasize surprise, shock, anger, disgust, etc. Just what on earth is going on here? Aw, what on earth! I just had this fixed, and now there's a dent in it! What on earth is wrong with you? Don't sneak up on me like that!

how, what, why, etc. on ˈearth...

how, why, etc. in the ˈworld...

(informal) used with questions to express the speaker’s surprise, anger, etc: How on earth did you know I was coming today when I didn’t know myself until the last minute? ♢ Why on earth would anyone give up such a good job?