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.
      [1913 Webster]

   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]

Moby Thesaurus II by Grady Ward, 1.0:

58 Moby Thesaurus words for "disprove":
   abjure, assert the contrary, belie, blow sky-high, blow up, break,
   confound, confute, contest, contradict, contravene, controvert,
   counter, cross, deflate, demolish, deny, destroy, disaffirm,
   disallow, disavow, disclaim, disconfirm, discredit, disown,
   dispute, evert, explode, expose, forswear, gainsay, impugn,
   invalidate, join issue upon, negate, negative, not accept,
   not admit, nullify, oppose, overthrow, overturn,
   prove the contrary, puncture, rebut, recant, refuse to admit,
   refute, renounce, repudiate, retract, revoke, shoot, show up,
   take back, take issue with, traverse, undercut