The Collaborative International Dictionary of English v.0.48:

Unchastity \Un*chas"ti*ty\, n.
   The quality or state of being unchaste; lewdness;
   incontinence.
   [1913 Webster]

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "unchastity":
   Cyrenaic hedonism, Cyrenaicism, amorality, appetite,
   appetitiveness, backsliding, carnality, criminality, delinquency,
   epicureanism, epicurism, ethical hedonism, evil, evil nature,
   hedonic calculus, hedonics, hedonism, immorality, impropriety,
   impurity, inappropriateness, indecency, indecorousness, indecorum,
   indelicacy, indiscreetness, indiscretion, inelegance, inelegancy,
   lady-killing, lechery, licentiousness, luxuriousness, luxury,
   moral delinquency, peccability, philander, philandering,
   pleasure principle, pleasure-seeking, prodigality,
   psychological hedonism, recidivism, sensualism, sensuality,
   sensualness, sybaritism, unangelicalness, uncleanness, ungodliness,
   ungoodness, unmorality, unrighteousness, unsaintliness,
   unseemliness, unvirtuousness, vice, viciousness, voluptuousness,
   wantonness, waywardness, wrongdoing