The Collaborative International Dictionary of English v.0.48:

Depravation \Dep`ra*va"tion\ (d[e^]p`r[.a]*v[=a]"sh[u^]n), n.
   [L. depravitio, from depravare: cf. F. d['e]pravation. See
   Deprave.]
   1. Detraction; depreciation. [Obs.]
      [1913 Webster]

            To stubborn critics, apt, without a theme,
            For depravation.                      --Shak.
      [1913 Webster]

   2. The act of depraving, or making anything bad; the act of
      corrupting.
      [1913 Webster]

   3. The state of being depraved or degenerated; degeneracy;
      depravity.
      [1913 Webster]

            The depravation of his moral character destroyed his
            judgment.                             --Sir G. C.
                                                  Lewis.
      [1913 Webster]

   4. (Med.) Change for the worse; deterioration; morbid
      perversion.

   Syn: Depravity; corruption. See Depravity.
        [1913 Webster]

WordNet (r) 3.0 (2006):

depravation
    n 1: moral perversion; impairment of virtue and moral
         principles; "the luxury and corruption among the upper
         classes"; "moral degeneracy followed intellectual
         degeneration"; "its brothels, its opium parlors, its
         depravity"; "Rome had fallen into moral putrefaction" [syn:
         corruption, degeneracy, depravation, depravity,
         putrefaction]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "depravation":
   abandon, abandonment, abjection, comedown, corruptedness,
   corruption, corruptness, debasement, decadence, decadency,
   declension, declination, decline, deformation, degeneracy,
   degenerateness, degeneration, degradation, demoralization,
   demotion, depravedness, depravity, depreciation, derogation,
   descent, deterioration, devolution, dissoluteness, downtrend,
   downturn, downward mobility, downward trend, drop, dying, ebb,
   effeteness, fading, failing, failure, failure of nerve, fall,
   falling-off, involution, lapse, loss of tone, moral pollution,
   moral turpitude, profligacy, regression, reprobacy, retrocession,
   retrogradation, retrogression, rottenness, slippage, slump,
   turpitude, wane