Hold your hands upwards, with arms bent and elbows by your sides, shrug and make your mouth wide (but closed) so you dimple your cheeks.
What on earth is that called?
That’s called a “shrug.” To describe it more completely, you’re going to have to use more than one word.
“He threw his hands up and shrugged, his face a mask of comic impotence.”
If you want to fit the whole thing into a single noun, you’re going to have to ask a German.
hunches shoulders, faces palms skyward, lowers head and adopts a facial expression intended to convey friendly dismay at being unable to be more helpful
“uh-nuh-uh?”
“In answer to the question, she mimed WTF.”
The facial part of it could be characterized as a moue.
I would describe it as a “supplicatory grimace”
Aufgedimpleschrug?
I asked Sid Caesar’s German professor.
Hmm. Not bad.