Source : Webster's Revised Unabridged Dictionary (1913)

Emperor \Em"per*or\, n. [OF. empereor, empereour, F. empereur,
   L. imperator, fr. imperare to command; in in + parare to
   prepare, order. See {Parade}, and cf. {Imperative},
   {Empress}.]
   The sovereign or supreme monarch of an empire; -- a title of
   dignity superior to that of king; as, the emperor of Germany
   or of Austria; the emperor or Czar of Russia.

   {Emperor goose} (Zo["o]l.), a large and handsome goose
      ({Philacte canagica}), found in Alaska.

   {Emperor moth} (Zo["o]l.), one of several large and beautiful
      bombycid moths, with transparent spots on the wings; as
      the American Cecropia moth ({Platysamia cecropia}), and
      the European species ({Saturnia pavonia}).

   {Emperor paper}. See under {Paper}.

   {Purple emperor} (Zo["o]l.), a large, strong British
      butterfly ({Apatura iris}).

Source : WordNet®

Apatura iris
     n : large European butterfly the male of which has wings shaded
         with purple [syn: {purple emperor}]