Source : Webster's Revised Unabridged Dictionary (1913)

Mask \Mask\, n.
   1. A person wearing a mask; a masker.

            The mask that has the arm of the Indian queen. --G.
                                                  W. Cable.

   2. (Sporting) The head or face of a fox.

   {Death mask}, a cast of the face of a dead person.

Source : WordNet®

death mask
     n : a cast taken from the face of a dead person