The Collaborative International Dictionary of English v.0.48:

Contradict \Con`tra*dict\, v. i.
   To oppose in words; to gainsay; to deny, or assert the
   contrary of, something.
   [1913 Webster]

         They . . . spake against those things which were spoken
         by Paul, contradicting and blaspheming.  --Acts xiii.
                                                  45.
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The Collaborative International Dictionary of English v.0.48:

Contradict \Con`tra*dict"\, v. t. [imp. & p. p. Contradicted;
   p. pr. & vb. n. Contradicting.] [L. contradictus, p. p. of
   contradicere to speak against; contra + dicere to speak. See
   Diction.]
   1. To assert the contrary of; to oppose in words; to take
      issue with; to gainsay; to deny the truth of, as of a
      statement or a speaker; to impugn.
      [1913 Webster]

            Dear Duff, I prithee, contradict thyself,
            And say it is not so.                 --Shak.
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            The future can not contradict the past.
                                                  --Wordsworth.
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   2. To be contrary to; to oppose; to resist. [Obs.]
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            No truth can contradict another truth. --Hooker.
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            A greater power than we can contradict
            Hath thwarted our intents.            --Shak.
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WordNet (r) 3.0 (2006):

contradict
    v 1: be in contradiction with [syn: contradict, belie,
         negate]
    2: deny the truth of [syn: contradict, negate, contravene]
    3: be resistant to; "The board opposed his motion" [syn:
       oppose, controvert, contradict]
    4: prove negative; show to be false [syn: negate,
       contradict] [ant: affirm, confirm, corroborate,
       substantiate, support, sustain]