The Collaborative International Dictionary of English v.0.48:

Refutation \Ref`u*ta"tion\ (r?f`?*t?"sh?n), n. [L. refutatio:
   cf. F. r['e]futation.]
   The act or process of refuting or disproving, or the state of
   being refuted; proof of falsehood or error; the overthrowing
   of an argument, opinion, testimony, doctrine, or theory, by
   argument or countervailing proof.
   [1913 Webster]

         Same of his blunders seem rather to deserve a flogging
         than a refutation.                       --Macaulay.
   [1913 Webster]

WordNet (r) 3.0 (2006):

refutation
    n 1: the speech act of answering an attack on your assertions;
         "his refutation of the charges was short and persuasive";
         "in defense he said the other man started it" [syn:
         refutation, defense, defence]
    2: any evidence that helps to establish the falsity of something
       [syn: disproof, falsification, refutation]
    3: the act of determining that something is false [syn:
       falsification, falsifying, disproof, refutation,
       refutal]

Moby Thesaurus II by Grady Ward, 1.0:

83 Moby Thesaurus words for "refutation":
   abjuration, abjurement, abrogation, absolute contradiction,
   annulment, answer, argument, argumentum, case, complete answer,
   confounding, confutation, cons, consideration, contradiction,
   contraremonstrance, contrary assertion, contravention,
   controversion, counteraccusation, counterblast, countercharge,
   counterclaim, countering, counterreply, counterstatement, crossing,
   defense, demolition, demurrer, denial, disaffirmation,
   disallowance, disavowal, disclaimer, disclamation, discrediting,
   disownment, disproof, effective rejoinder, elenchus, exception,
   forswearing, gainsaying, ignoratio elenchi, impugnment,
   nullification, objection, overthrow, overthrowal, plaidoyer, plea,
   pleading, pleadings, pros, pros and cons, reason, rebuttal,
   rebutter, recantation, refutal, rejoinder, renunciation,
   replication, reply, repudiation, response, retractation,
   retraction, revocation, riposte, special demurrer,
   special pleading, squelch, statement of defense, subversion,
   surrebuttal, surrebutter, surrejoinder, talking point, undermining,
   upset, upsetting