The Collaborative International Dictionary of English v.0.48:

Disguise \Dis*guise"\, n.
   1. A dress or exterior put on for purposes of concealment or
      of deception; as, persons doing unlawful acts in disguise
      are subject to heavy penalties.
      [1913 Webster]

            There is no passion which steals into the heart more
            imperceptibly and covers itself under more
            disguises, than pride.                --Addison.
      [1913 Webster]

   2. Artificial language or manner assumed for deception; false
      appearance; counterfeit semblance or show.
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            That eye which glances through all disguises. --D.
                                                  Webster.
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   3. Change of manner by drink; intoxication. --Shak.
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   4. A masque or masquerade. [Obs.]
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            Disguise was the old English word for a masque. --B.
                                                  Jonson.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Disguise \Dis*guise"\ (?; 232), v. t. [imp. & p. p. Disguised;
   p. pr. & vb. n. Disguising.] [OE. desguisen, disgisen,
   degisen, OF. desguisier, F. d['e]guiser; pref. des- (L. dis-)
   + guise. See Guise.]
   1. To change the guise or appearance of; especially, to
      conceal by an unusual dress, or one intended to mislead or
      deceive.
      [1913 Webster]

            Bunyan was forced to disguise himself as a wagoner.
                                                  --Macaulay.
      [1913 Webster]

   2. To hide by a counterfeit appearance; to cloak by a false
      show; to mask; as, to disguise anger; to disguise one's
      sentiments, character, or intentions.
      [1913 Webster]

            All God's angels come to us disguised. --Lowell.
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   3. To affect or change by liquor; to intoxicate.
      [1913 Webster]

            I have just left the right worshipful, and his
            myrmidons, about a sneaker of five gallons; the
            whole magistracy was pretty well disguised before I
            gave them the ship.                   --Spectator.

   Syn: To conceal; hide; mask; dissemble; dissimulate; feign;
        pretend; secrete. See Conceal.
        [1913 Webster]

WordNet (r) 3.0 (2006):

disguise
    n 1: an outward semblance that misrepresents the true nature of
         something; "the theatrical notion of disguise is always
         associated with catastrophe in his stories" [syn:
         disguise, camouflage]
    2: any attire that modifies the appearance in order to conceal
       the wearer's identity
    3: the act of concealing the identity of something by modifying
       its appearance; "he is a master of disguise" [syn:
       disguise, camouflage]
    v 1: make unrecognizable; "The herb masks the garlic taste"; "We
         disguised our faces before robbing the bank" [syn:
         disguise, mask]

Moby Thesaurus II by Grady Ward, 1.0:

190 Moby Thesaurus words for "disguise":
   accouter, acting, affect, affectation, appearance, assume,
   attitudinizing, bad copy, bad likeness, ballet skirt, becloud,
   befog, belie, blanket, blind, bluff, bluffing, burlesque, buskin,
   camouflage, cap and bells, caparison, caricature, charade,
   cheating, cloak, cloud, color, coloring, conceal, contrast,
   costume, counterfeit, cover, cover up, cover-up, curtain, deceive,
   deception, delusion, difference, disparity, dissemblance,
   dissemble, dissembling, dissimilarity, dissimilate, dissimilation,
   dissimilitude, dissimulate, dissimulation, distort,
   distract attention from, divergence, diversity, domino, dress up,
   eclipse, embellish, embroider, ensconce, enshroud, envelop, equip,
   exaggerate, facade, face, fake, fakery, faking, false air,
   false colors, false face, false front, false show, falsify,
   falsity, feign, feigning, feint, fit, fit out, form, four-flushing,
   fraud, front, fudge, garble, getup, gild, gilt, gloss, gloss over,
   guise, habit, hide, humbug, humbuggery, identity, imposture,
   incognito, incommensurability, incomparability, keep under cover,
   make-believe, makeup, mask, masque, masquerade, mere caricature,
   meretriciousness, miscite, miscolor, misquote, misreport,
   misrepresent, misstate, misteach, motley, mummery, nonuniformity,
   obfuscate, obscure, occult, ostentation, outfit, outward show,
   overdraw, overstate, pageant, parody, pervert, playacting,
   poor imitation, pose, posing, posture, pretend, pretense,
   pretension, pretentiousness, pretext, protective coloration,
   put-on, representation, rig, rig out, rig up, screen, seeming,
   semblance, shade, sham, show, shroud, simulacrum, simulate,
   simulation, slant, slur over, smoke screen, sock, speciousness,
   strain, suit, tights, titivate, travesty, trick out, turn out,
   tutu, twist, understate, uniform, unlikeness, unresemblance,
   unsameness, unsimilarity, varnish, vary, veil, veneer, visor,
   vizard, vizard mask, warp, whitewash, window dressing, wraps,
   wrench