Source : Webster's Revised Unabridged Dictionary (1913)

Monarch \Mon"arch\, n. [F. monarque, L. monarcha, fr. Gr. ?, ?;
   ? alone + ? to be first, rule, govern. See {Archi-}.]
   1. A sole or supreme ruler; a sovereign; the highest ruler;
      an emperor, king, queen, prince, or chief.

            He who reigns Monarch in heaven, . . . upheld by old
            repute.                               --Milton.

   2. One superior to all others of the same kind; as, an oak is
      called the monarch of the forest.

   3. A patron deity or presiding genius.

            Come, thou, monarch of the vine, Plumpy Bacchus.
                                                  --Shak.

   4. (Zo["o]l.) A very large red and black butterfly ({Danais
      Plexippus}); -- called also {milkweed butterfly}.

Source : WordNet®

milkweed butterfly
     n : large migratory American butterfly having deep orange wings
         with black and white markings; the larvae feed on
         milkweed [syn: {monarch}, {monarch butterfly}, {Danaus
         plexippus}]