The Collaborative International Dictionary of English v.0.48:
Low-necked \Low"-necked`\, a. Cut low in the neck; decollete; low-cut; -- said of a woman's dress. [1913 Webster]WordNet (r) 3.0 (2006):
low-necked adj 1: (of a garment) having a low-cut neckline; "a low-cut neckline" [syn: decollete, low-cut, low-necked]