what on earth is this?; what the heck is this?
Colloquial, informal exclamation expressing surprise or bewilderment at something unexpected. Often used by men, but not exclusively. Similar to なんだこれは but more casual and emphatic.
See also: なんだこれは
What on earth is this?! I've never seen anything like it.
There was something weird on the desk, and I thought, 'What the heck is this?'