Buttso anyway!
If that is the area where you get fat, you can lose fat with more cardio/better diet, and you can make the glute just strong and huge, but it will almost certainly never look smoothe and defined. My butt is hideous, no matter what, even when I was anorexic, while my stomach stays flat as a board even when I am over ideal weight and returned to normal 2 months after childbirth.
Some of this is genetic, I'm afraid.