The facial expression achieved when you're taking a gigantic size bite out of a hamburger/hotdog and you expect ketchup but itstead it's fucking loaded with mustard.
"You should have seen that kid's mustard face after I falcon punched him in the testicles. Priceless."
"That old woman had a perfect mustard face after I crop dusted that elevator."
By Helene
Mustard Face
someone who is clearly pissed off, shitty and in a mood and it blatantly shows. They have a face like they have eaten a spoon full of mustard
