What I can salvage from Baby Got Back with a clearer definition and trope and little room for gushing. Needs a Better Title. And description, I can't write. Also will contain bending over as part of the trope. Needs help.
The female rear end is one of the more sexualized body parts, and it's usually associated with youth, fertility and beauty. Not too mention stop men dead in their tracks.
This is where a female character with nice assets
comes in. They get compliments, and praise and they know they have a nice rear end. And they can use it too get whatever they want. Either with a seductive walk, and a convenient "OOPS!" bending over. The men usually can't help themselves and the female characters then can either laugh at their utter helplessness. They can even use their wiles for good (as in gaining somewhat they want) or evil
or or just simply for the attention.
Not that this is limited to female characters, of course.
This is not character with nice ass, or even character with a lot of Male Gaze
camera shots on their butts. It's explicitly mentioned In-Universe