Noun. Originally Miami's Ugly Girl(s). But, now that the term is used more generally, its new definition is: Mad Ugly Girl(s). MUGs are usually to be avoided, though they have certain uses. Examples of their functions include; cup holders, gag inducers, and, at times, sources of comedic entertainment.
Other forms of MUG include; MUGgy (environment filled with MUGs), MUGgy (adjective or adverb form of MUG), MUGish (partially MUG like), and MUGish (adjective or adverb form of MUG)
Guy 1: Dude,check out that fat chick
Guy 2: Wow, what a MUG
Guy 1: Since when did ___ get so MUGgy?
Guy 2: I don't know bro, I haven't seen a single decent looking girl in here all night.