mean-mugging

Mean-mugging is giving someone a hard, hostile stare—the kind of look that signals disapproval, aggression, or intimidation.

The term combines mean with mugging, where mug is slang for face, so to mean-mug is literally to make a mean face at someone.

It's common in contexts where confrontation is implied but not yet verbal or physical: Why is that dude mean-mugging me from across the bar?

The look often serves as a challenge or warning.