The Collaborative International Dictionary of English v.0.48:

Denial \De*ni"al\, n. [See Deny.]
   1. The act of gainsaying, refusing, or disowning; negation;
      -- the contrary of affirmation.
      [1913 Webster]

            You ought to converse with so much sincerity that
            your bare affirmation or denial may be sufficient.
                                                  --Bp.
                                                  Stillingfleet.
      [1913 Webster]

   2. A refusal to admit the truth of a statement, charge,
      imputation, etc.; assertion of the untruth of a thing
      stated or maintained; a contradiction.
      [1913 Webster]

   3. A refusal to grant; rejection of a request.
      [1913 Webster]

            The commissioners, . . . to obtain from the king's
            subjects as much as they would willingly give, . . .
            had not to complain of many peremptory denials.
                                                  --Hallam.
      [1913 Webster]

   4. A refusal to acknowledge; disclaimer of connection with;
      disavowal; -- the contrary of confession; as, the denial
      of a fault charged on one; a denial of God.
      [1913 Webster]

   Denial of one's self, a declining of some gratification;
      restraint of one's appetites or propensities; self-denial.
      [1913 Webster]

WordNet (r) 3.0 (2006):

denial
    n 1: the act of refusing to comply (as with a request); "it
         resulted in a complete denial of his privileges"
    2: the act of asserting that something alleged is not true [syn:
       denial, disaffirmation]
    3: (psychiatry) a defense mechanism that denies painful thoughts
    4: renunciation of your own interests in favor of the interests
       of others [syn: abnegation, self-abnegation, denial,
       self-denial, self-renunciation]
    5: a defendant's answer or plea denying the truth of the charges
       against him; "he gave evidence for the defense" [syn:
       defense, defence, denial, demurrer] [ant: criminal
       prosecution, prosecution]

Moby Thesaurus II by Grady Ward, 1.0:

234 Moby Thesaurus words for "denial":
   Eighteenth Amendment, Prohibition Party, Volstead Act, abjuration,
   abjurement, abnegation, abrogation, absolute contradiction,
   abstaining, agnosticism, annulment, answer, argument, atheism, ban,
   bereavement, bucking, challenge, chucking, chucking out,
   complete answer, confounding, confutation, constraint, contempt,
   contention, contraband, contradiction, contraposition,
   contrary assertion, contravention, contraversion, controversion,
   cost, counteraction, countering, counterstatement, counterworking,
   crosscurrent, crossing, damage, dead loss, debit, declension,
   declination, declinature, declining, defense, demolition, demurrer,
   denudation, deprivation, despisal, despising, despoilment,
   destruction, detriment, disaffirmation, disagreement, disallowance,
   disapproval, disavowal, disbelief, discard, disclaimer,
   disclamation, discounting, discredit, discrediting, dismissal,
   disobedience, disowning, disownment, dispossession, disproof,
   disregard, dissent, divestment, effective rejoinder, embargo,
   exception, exclusion, expatriation, expense, forbearance,
   forbiddance, forbidden fruit, forbidding, forfeit, forfeiture,
   forswearing, frugality, gainsaying, golden mean, head wind, heresy,
   holding back, ignoring, impugnation, impugnment,
   inability to believe, incredulity, index, index expurgatorius,
   index librorum prohibitorum, infidelity, inhibition, injunction,
   injury, interdict, interdiction, interdictum, law, loser, losing,
   losing streak, loss, minimifidianism, misbelief, moderateness,
   moderation, nay, negation, negative, negative answer, nix, no,
   no-no, nonacceptance, nonapproval, nonbelief, noncompliance,
   nonconsent, nonconsideration, nonobservance, nothing in excess,
   nullification, nullifidianism, objection, opposing, opposition,
   opposure, oppugnation, overthrow, overthrowal, palinode, palinody,
   passing by, perdition, plea, pleading, preclusion, prevention,
   privation, prohibition, prohibitory injunction, proscription,
   putting away, putting out, rebuff, rebutment, rebuttal,
   recantation, refraining, refusal, refutal, refutation, rejection,
   reneging, renouncement, renunciation, reply, repression,
   repudiation, repulse, resistance, response, restraint,
   restrictive covenants, retention, retractation, retraction,
   revocation, revokement, riposte, robbery, ruin, ruling out,
   sacrifice, scouting, self, self-control, self-denial,
   self-discipline, self-mastery, self-restraint, soberness, sobriety,
   sophrosyne, special demurrer, special pleading, spoliation,
   spurning, squelch, standing against, statement of defense, statute,
   stripping, subversion, sumptuary laws, suppression, taboo,
   taking away, temperance, temperateness, throwing out, thumbs-down,
   total loss, traversal, turndown, turning out, unbelief,
   unbelievingness, undercurrent, undermining, unsaying,
   unwillingness, upset, upsetting, veto, withdrawal, withholding,
   zoning, zoning laws



Bouvier's Law Dictionary, Revised 6th Ed (1856):

DENIAL, pleading. To traverse the statement of the opposite party a defence.
See Defence; Traverse.