Source : Webster's Revised Unabridged Dictionary (1913)

Rebuff \Re*buff"\, n. [It. ribuffo, akin to ribuffare to
   repulse; pref. ri- (L. re-) + buffo puff. Cf. {Buff} to
   strike, {Buffet} a blow.]
   1. Repercussion, or beating back; a quick and sudden
      resistance.

            The strong rebuff of some tumultuous cloud.
                                                  --Milton.

   2. Sudden check; unexpected repulse; defeat; refusal;
      repellence; rejection of solicitation.

Rebuff \Re*buff"\, v. t. [imp. & p. p. {Rebuffed}; p. pr. & vb.
   n. {Rebuffing}.]
   To beat back; to offer sudden resistance to; to check; to
   repel or repulse violently, harshly, or uncourteously.

Source : WordNet®

rebuff
     n 1: a deliberate discourteous act (usually as an expression of
          anger or disapproval) [syn: {slight}]
     2: an instance of driving away or warding off [syn: {snub}, {repulse}]
     v 1: reject outright and bluntly; "She snubbed his proposal"
          [syn: {snub}, {repel}]
     2: force or drive back; "repel the attacker"; "fight off the
        onslaught"; "rebuff the attack" [syn: {repel}, {repulse},
        {fight off}, {drive back}]