The word "curvy" should be used to describe a woman with large breasts, a small waist, and a full bottom. REAL curvy women are Kim Kardashian, Scarlett Johansson, and Marilyn Monroe.
HOWEVER, in teen magazines like Seventeen and Cosmo Girl, "curvy" is used as a synonym for fat, so that fat girls feel better about their figures.
With a 27-inch waist and 38 inch hips and breasts, Kim Kardashian is truly curvy.
Overweight girls who wear a size 14 in jeans are not curvy, but plain old fat.