The Collaborative International Dictionary of English v.0.48:

Belittle \Be*lit"tle\, v. t. [imp. & p. p. Belittled; p. pr. &
   vb. n. Belittling.]
   To make little or less in a moral sense; to speak of in a
   depreciatory or contemptuous way. --T. Jefferson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

belittling
    adj 1: tending to diminish or disparage; "belittling comments";
           "managed a deprecating smile at the compliment";
           "deprecatory remarks about the book"; "a slighting
           remark" [syn: belittling, deprecating, deprecative,
           deprecatory, depreciative, depreciatory,
           slighting]
    n 1: a belittling comment [syn: denigration, belittling]
    2: the act of belittling

Moby Thesaurus II by Grady Ward, 1.0:

49 Moby Thesaurus words for "belittling":
   abusive, back-biting, belittlement, bitchy, calumniatory,
   calumnious, catty, censorious, comedown, contempt, contemptuous,
   contumelious, decrial, defamatory, deprecatory, depreciation,
   depreciative, depreciatory, derisive, derisory, derogation,
   derogative, derogatory, detraction, detractory, disapproval,
   discrediting, disgrace, disparagement, disparaging, faint praise,
   indignity, knocking, libelous, lukewarm support, minification,
   minimization, minimizing, pejorative, putting down, qualification,
   ridiculing, scandalous, scurrile, scurrilous, slanderous,
   slighting, sour grapes, vilifying