The Collaborative International Dictionary of English v.0.48:

Masquerade \Mas`quer*ade"\, v. i. [imp. & p. p. Masqueraded;
   p. pr. & vb. n. Masquerading.]
   [1913 Webster]
   1. To assemble in masks; to take part in a masquerade.
      [1913 Webster]

   2. To frolic or disport in disquise; to make a pretentious
      show of being what one is not.
      [1913 Webster]

            A freak took an ass in the head, and he goes into
            the woods, masquerading up and down in a lion's
            skin.                                 --L'Estrange.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Masquerade \Mas`quer*ade"\, n. [F. mascarade, fr. Sp. mascarada,
   or It. mascherata. See Mask.]
   [1913 Webster]
   1. An assembly of persons wearing masks, and amusing
      themselves with dancing, conversation, or other
      diversions.
      [1913 Webster]

            In courtly balls and midnight masquerades. --Pope.
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   2. A dramatic performance by actors in masks; a mask. See 1st
      Mask, 4. [Obs.]
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   3. Acting or living under false pretenses; concealment of
      something by a false or unreal show; pretentious show;
      disguise.
      [1913 Webster]

            That masquerade of misrepresentation which
            invariably accompanied the political eloquence of
            Rome.                                 --De Quincey.
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   4. A Spanish diversion on horseback.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Masquerade \Mas`quer*ade"\, v. t.
   To conceal with masks; to disguise. "To masquerade vice."
   --Killingbeck.
   [1913 Webster]

WordNet (r) 3.0 (2006):

masquerade
    n 1: a party of guests wearing costumes and masks [syn:
         masquerade, masquerade party, masque, mask]
    2: a costume worn as a disguise at a masquerade party [syn:
       fancy dress, masquerade, masquerade costume]
    3: making a false outward show; "a beggar's masquerade of
       wealth"
    v 1: take part in a masquerade
    2: pretend to be someone or something that you are not; "he is
       masquerading as an expert on the internet"; "This silly novel
       is masquerading as a serious historical treaty"