Busty

busty 

To have larger breasts, big tits, etc.

busty 

A girl who's apparent ratio of boobs to body is fairly high. A 4 foot 11 inch girl with C cup boobs could be considered very busty indeed.

In the porn world, Busty is often used to describe girls with large breasts that don't quite make it into the big tits category. That space between average and large.