The Collaborative International Dictionary of English v.0.48:

Detraction \De*trac"tion\, n. [F. d['e]traction, L. detractio.]
   1. A taking away or withdrawing. [Obs.]
      [1913 Webster]

            The detraction of the eggs of the said wild fowl.
                                                  --Bacon.
      [1913 Webster]

   2. The act of taking away from the reputation or good name of
      another; a lessening or cheapening in the estimation of
      others; the act of depreciating another, from envy or
      malice; calumny.

   Syn: Depreciation; disparagement; derogation; slander;
        calumny; aspersion; censure.
        [1913 Webster]

WordNet (r) 3.0 (2006):

detraction
    n 1: a petty disparagement [syn: detraction, petty
         criticism]
    2: the act of discrediting or detracting from someone's
       reputation (especially by slander); "let it be no detraction
       from his merits to say he is plainspoken"

Moby Thesaurus II by Grady Ward, 1.0:

24 Moby Thesaurus words for "detraction":
   aspersion, backbiting, backstabbing, belittlement, calumniation,
   calumny, character assassination, damage, defamation, depreciation,
   disparagement, harm, hurt, injury, injustice, libel, libeling,
   maligning, scandal, slander, sycophancy, tale, vilification,
   wrong