Mean mug

[PussyCat]

to give someone the evil eye and to stair them down.

[Jessica]

to look at someone in a mean way

[Zipporah Schumaker]

to stare someone down in a bad way. to ask someone if they wanna fight using eye contact.

[Donald Trump]

Noun. An aggravated or angry facial expression.

A prolonged, directed mean mug is often enough either start or avoid physical altercation.

Verb. To maintain an angry facial expression.

ref: www.meanestmug.com