The Collaborative International Dictionary of English v.0.48:

Derogation \Der`o*ga"tion\, n. [L. derogatio: cf. F.
   d['e]rogation.]
   1. The act of derogating, partly repealing, or lessening in
      value; disparagement; detraction; depreciation; --
      followed by of, from, or to.
      [1913 Webster]

            I hope it is no derogation to the Christian
            religion.                             --Locke.
      [1913 Webster]

            He counted it no derogation of his manhood to be
            seen to weep.                         --F. W.
                                                  Robertson.
      [1913 Webster]

   2. (Stock Exch.) An alteration of, or subtraction from, a
      contract for a sale of stocks.
      [1913 Webster]

WordNet (r) 3.0 (2006):

derogation
    n 1: a communication that belittles somebody or something [syn:
         disparagement, depreciation, derogation]
    2: (law) the partial taking away of the effectiveness of a law;
       a partial repeal or abolition of a law; "any derogation of
       the common law is to be strictly construed"

Moby Thesaurus II by Grady Ward, 1.0:

78 Moby Thesaurus words for "derogation":
   attrition, belittling, comedown, contempt, curtailment, cut,
   cutting, debasement, decadence, decadency, declension, declination,
   decline, decrease, decrement, decrial, deformation, degeneracy,
   degenerateness, degeneration, degradation, demotion, depletion,
   depravation, depravedness, depreciation, descent, deterioration,
   detraction, devolution, diminution, dip, disapproval, discrediting,
   disgrace, disparagement, downtrend, downturn, downward mobility,
   downward trend, drop, dying, ebb, effeteness, extraction, fading,
   failing, failure, failure of nerve, faint praise, fall,
   falling-off, impairment, indignity, involution, knocking, lapse,
   lessening, loss of tone, lukewarm support, minimizing,
   putting down, reduction, regression, remission, retraction,
   retrenchment, retrocession, retrogradation, retrogression,
   shortening, shrinkage, slighting, slippage, slump, sour grapes,
   truncation, wane



Bouvier's Law Dictionary, Revised 6th Ed (1856):

DEROGATION, civil law. The partial abrogation of a law; to derogate from a
law is to enact something which is contrary to it; to abrogate a law is' to
abolish it entirely. Dig. lib. 50, t. 17, 1. 102. See Abrogation.