The "Hinge" is the bend or crease in the jeans were the ass joins the leg in hot females. The hinge is most prominent in girls that are adourning jeans accompanied by a nice pair of Uggs. The hinge is not very complex, but it can be appreciated and ranked as any other female characteristic may be ranked. The hinge may also be considered the liasion of the leg and butt. It is most noticeable when the girl is standing...the girl's butt will overlap her hamstring causing a hinge or crease. It is also the spot in which a tanning bed will not reach.
Check out that chick in those skinny jeans and UGGs...her hinge is so nice.
The part of a female's anatomy where the butt meets the upper leg and overhangs, often creating a crease, if the former is large enough. The size of this overhang of the booty is dependent on their size and the protrusion of the arsecheeks.
(At the beach)
A: Hey bro, check out the hinge on her!
B: Goddayum, I'd open that out in no time.