The Collaborative International Dictionary of English v.0.48:

Disprove \Dis*prove"\, v. t. [imp. & p. p. Disproved; p. pr. &
   vb. n. Disproving.] [Pref. dis- + prove: cf. OF.
   desprover.]
   1. To prove to be false or erroneous; to confute; to refute.
      [1913 Webster]

            That false supposition I advanced in order to
            disprove it.                          --Atterbury.
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   2. To disallow; to disapprove of. [Obs.] --Stirling.
      [1913 Webster]

WordNet (r) 3.0 (2006):

disprove
    v 1: prove to be false; "The physicist disproved his colleagues'
         theories" [syn: disprove, confute] [ant: demonstrate,
         establish, prove, shew, show]