disparager

from WordNet (r) 3.0 (2006)

disparager
    n 1: one who disparages or belittles the worth of something
         [syn: {detractor}, {disparager}, {depreciator}, {knocker}]

from The Collaborative International Dictionary of English v.0.48

disparager \dis*par"a*ger\, n.
   One who disparages or dishonors; one who vilifies or
   disgraces.
   [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

22 Moby Thesaurus words for "disparager":
      Thersites, backbiter, belittler, calumniator, caustic critic,
      cynic, debunker, decrier, defamer, deflater, depreciator,
      derogator, detractor, hatchet man, knocker, libeler, muckraker,
      mudslinger, railer, slanderer, social critic, traducer

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