The face made when you are pissed to the point where you look like you just sucked a lemon dry.
The act of scrunching your face to the point where it is so ugly that your body counter acts it with pain.
Me: aye, you better chill out.
Me: Bruh, that dude got a lemon face! He ain't playin.
You: Oh, shit RUN!!
Me: DAMN! whats that smell?!?!
you: SHIT!!! LEMON FACE!!