An ordinary or unappealingly looking woman (or man in some cases if he is short -- see Choad) who has a broad face and short dumpy body though usually endowed with larger breasts than normal. Mugwumps will also usually have short stumpy digits.
She is a very nice girl but I can't date her because she's a mugwump.
A small, swamp-dwelling creature that subsists on skunk cabbage and likes to burrow. Mugwumps can be identified by the low "wumpwumpwumpwump" sound they make, and by their fear of any jumps other than little ones.
I'm making skunk cabbage flambé for dessert tonight because the mugwumps from the bog next door are coming over for dinner.