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):

belittle
    v 1: cause to seem less serious; play down; "Don't belittle his
         influence" [syn: minimize, belittle, denigrate,
         derogate]
    2: express a negative opinion of; "She disparaged her student's
       efforts" [syn: disparage, belittle, pick at] [ant:
       blandish, flatter]
    3: lessen the authority, dignity, or reputation of; "don't
       belittle your colleagues" [syn: diminish, belittle]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "belittle":
   bedwarf, bring down, bring into discredit, bring low, criticize,
   cry down, de-emphasize, debase, decry, degrade, denigrate,
   deprecate, depreciate, derogate, derogate from, detract from,
   diminish, disapprove of, discount, discredit, disgrace, disparage,
   dispraise, downgrade, downplay, dwarf, hold in contempt, knock,
   lessen, make light of, make little of, make nothing of, minify,
   minimize, misestimate, misprize, mitigate, play down, pooh-pooh,
   put down, reduce, reflect discredit upon, run down, sell short,
   set at naught, set little by, shrug off, slight, speak ill of,
   submit to indignity, think little of, think nothing of, trivialize,
   underestimate, underplay, underprize, underrate, underreckon,
   undervalue, write off