a gesture in which the palm of one's hand is brought to one's face as an expression of dismay, exasperation, embarrassment, etc.

I'm pretty sure said friend now thinks Anne and I are dating—facepalm!

you have to see this one to believe it—it definitely merits the double facepalm

bring the palm of one's hand to one's face as an expression of dismay, exasperation, embarrassment, etc.

did anyone else facepalm during this scene?