Answer: facepalm

AnswerCrossword Clue
FACEPALM

Gesture of embarrassed disappointment

FACEPALM

Nonverbal equivalent of "You have got to be kidding me!"

FACEPALM

Alternative to a head slap

FACEPALM
[I'm such an idiot!]
FACEPALM
[I can't believe that just happened!]