Face-forearm
You're so mortified you use your forearm to slap your face like it's a slap fight and you're the loser.
When I told my crush I liked him and he said he was already taken. Face-forearm. #crushfail
I tripped in front of my whole class. Face-forearm. #tripdisaster
My dog stole my sandwich and I had to eat a burger. Face-forearm. #sandwichtheft