When a female (usually an older woman, particularly a mother) wears unflattering, waist high jeans that give the buttocks a flat, unappealing look. It may sometimes entail wearing sweat pants bought from your local Walmart. Also note the buttocks may possibly look as if there is a large amount of cellulite. Either way, you don't want that.
Those Dungarees totally give that girl a mom butt, but I am desperate..