1. 
[syn: decollete, low-cut, low-necked]
2.  having a low-cut back; 
- Example: "a backless dress"
The Collaborative International Dictionary of English v.0.48:
low-cut \low-cut\ adj.
   1. having a neckline low enough to expose part of the breast;
      -- of a woman's garment; as, a low-cut party dress.
   Syn: decollete, low-necked.
        [WordNet 1.5 +PJC]
   2. having a back exposing skin between the shoulder blades.
      [WordNet 1.5 +PJC] lowdown
WordNet (r) 3.0 (2006):
low-cut
    adj 1: (of a garment) having a low-cut neckline; "a low-cut
           neckline" [syn: decollete, low-cut, low-necked]
    2: having a low-cut back; "a backless dress"