low-cut

from 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"

from 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