Backless dress
From wipipedia.org
A backless dress is one cut so low at the back that the wearer's back is completely exposed. It may even reveal rear cleavage. The idea is to keep most of your front covered to look classy, while revealing enough skin to look daring and sexy.
Obviously, if a normal bra is worn, the rear strap will be visible. To get around this, it may be worn without a bra, or with a specially designed low-back bra or an adhesive bra.
