Giving someone a dirty look. Looking at someone like you're mad at them.
I haven't done nothing to you....... why you be ugly muggin' me?
by Jim Hancock Productions August 28, 2006
A face that is undisputedly ugly and resembles that of a mug or cup.
"You are an ugly mug.. and that is just a normal mug."
by JENNNNNNNNNIFER January 29, 2008
The face of someone who is not actually ugly at all, but who acts despicably in public.
I was checking up on my boyfriend online and saw his ugly mug looking back at me from his new profile on match.com.
by La-La-Land August 28, 2011