Source : Webster's Revised Unabridged Dictionary (1913)

Masked \Masked\, a.
   1. Wearing a mask or masks; characterized by masks;
      cincealed; hidden.

   2. (Bot.) Same as {Personate}.

   3. (Zo["o]l.) Having the anterior part of the head differing
      decidedly in color from the rest of the plumage; -- said
      of birds.

   {Masked ball}, a ball in which the dancers wear masks.

   {Masked battery} (Mil.), a battery so placed as not to be
      seen by an enemy until it opens fire. --H. L. Scott.

   {Masked crab} (Zo["o]l.), a European crab ({Corystes
      cassivelaunus}) with markings on the carapace somewhat
      resembling a human face.

   {Masked pig} (Zo["o]l.), a Japanese domestic hog ({Sus
      pliciceps}). Its face is deeply furrowed.

Source : WordNet®

masked ball
     n : a ball at which guests wear costumes and masks [syn: {masquerade
         ball}, {fancy-dress ball}]