The Collaborative International Dictionary of English v.0.48:
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,
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).