The Collaborative International Dictionary of English v.0.48:
Unchaste \Un*chaste"\, a. Not chaste; not continent; lewd. -- Un*chaste"ly, adv. -- Un*chaste"ness, n. [1913 Webster]WordNet (r) 3.0 (2006):
unchaste adj 1: not chaste; "unchaste conduct" [ant: chaste]