Sometimes you don't want to wear a bra, but you don't want to skip support either. Or, maybe the top you're wearing is difficult to style with a bra underneath. That's where built-in bras come in. No more worrying about visible bra straps or finding the right bra to wear under certain outfits. But what exactly is a built-in bra, and how does it differ from other bra styles? Honeylove explains. A built-in bra is a bra that is integrated directly into a garment, such as a tank top, dress or bodysuit.