Demi bras, also known as balconette bras, are a half-cup bra style with
wide-set straps and a horizontal bust line. Often seamed or boned, they
promote cleavage and a frame-like effect. These offer less support but
enable low-cut garments to be worn without the bra being seen. Demi bras
may be designed to provide lift as do push-up bras.
In other words, it's an old style bra that pushes your boobs up and closer together.
In other words, it's an old style bra that pushes your boobs up and closer together.
A Pictorial Tribute to the "Demi Bra":