The Collaborative International Dictionary of English v.0.48:

Disdain \Dis*dain"\ (?; 277), n. [OE. desdain, disdein, OF.
   desdein, desdaing, F. d['e]dain, fr. the verb. See Disdain,
   v. t.]
   1. A feeling of contempt and aversion; the regarding anything
      as unworthy of or beneath one; scorn.
      [1913 Webster]

            How my soul is moved with just disdain! --Pope.
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   Note: Often implying an idea of haughtiness.
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               Disdain and scorn ride sparkling in her eyes.
                                                  --Shak.
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   2. That which is worthy to be disdained or regarded with
      contempt and aversion. [Obs.]
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            Most loathsome, filthy, foul, and full of vile
            disdain.                              --Spenser.
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   3. The state of being despised; shame. [Obs.] --Shak.

   Syn: Haughtiness; scorn; contempt; arrogance; pride. See
        Haughtiness.
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The Collaborative International Dictionary of English v.0.48:

Disdain \Dis*dain"\ (?; 277), v. t. [imp. & p. p. Disdained;
   p. pr. & vb. n. Disdaining.] [OE. disdainen, desdainen, OF.
   desdeigner, desdaigner, F. d['e]daigner; des- (L. dis-) +
   daigner to deign, fr. L. dignari to deem worthy. See
   Deign.]
   1. To think unworthy; to deem unsuitable or unbecoming; as,
      to disdain to do a mean act.
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            Disdaining . . . that any should bear the armor of
            the best knight living.               --Sir P.
                                                  Sidney.
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   2. To reject as unworthy of one's self, or as not deserving
      one's notice; to look with scorn upon; to scorn, as base
      acts, character, etc.
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            When the Philistine . . . saw David, he disdained
            him; for he was but a youth.          --1 Sam. xvii.
                                                  42.
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            'T is great, 't is manly to disdain disguise.
                                                  --Young.

   Syn: To contemn; despise; scorn. See Contemn.
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The Collaborative International Dictionary of English v.0.48:

Disdain \Dis*dain"\, v. i.
   To be filled with scorn; to feel contemptuous anger; to be
   haughty.
   [1913 Webster]

         And when the chief priests and scribes saw the marvels
         that he did . . . they disdained.        --Genevan
                                                  Testament
                                                  (Matt. xxi.
                                                  15).
   [1913 Webster]

WordNet (r) 3.0 (2006):

disdain
    n 1: lack of respect accompanied by a feeling of intense
         dislike; "he was held in contempt"; "the despite in which
         outsiders were held is legendary" [syn: contempt,
         disdain, scorn, despite]
    2: a communication that indicates lack of respect by patronizing
       the recipient [syn: condescension, disdain, patronage]
    v 1: look down on with disdain; "He despises the people he has
         to work for"; "The professor scorns the students who don't
         catch on immediately" [syn: contemn, despise, scorn,
         disdain]
    2: reject with contempt; "She spurned his advances" [syn:
       reject, spurn, freeze off, scorn, pooh-pooh,
       disdain, turn down]