Source : Webster's Revised Unabridged Dictionary (1913)

Admiral \Ad"mi*ral\, n. [OE. amiral, admiral, OF. amiral,
   ultimately fr. Ar. am[=i]r-al-bahr commander of the sea; Ar.
   am[=i]r is commander, al is the Ar. article, and am[=i]r-al,
   heard in different titles, was taken as one word. Early forms
   of the word show confusion with L. admirabilis admirable, fr.
   admirari to admire. It is said to have been introduced into
   Europe by the Genoese or Venetians, in the 12th or 13th
   century. Cf. {Ameer}, {Emir}.]
   1. A naval officer of the highest rank; a naval officer of
      high rank, of which there are different grades. The chief
      gradations in rank are admiral, vice admiral, and rear
      admiral. The admiral is the commander in chief of a fleet
      or of fleets.

   2. The ship which carries the admiral; also, the most
      considerable ship of a fleet.

            Like some mighty admiral, dark and terrible, bearing
            down upon his antagonist with all his canvas
            straining to the wind, and all his thunders roaring
            from his broadsides.                  --E. Everett.

   3. (Zo["o]l.) A handsome butterfly ({Pyrameis Atalanta}) of
      Europe and America. The larva feeds on nettles.

   {Admiral shell} (Zo["o]l.), the popular name of an ornamental
      cone shell ({Conus admiralis}).

   {Lord High Admiral}, a great officer of state, who (when this
      rare dignity is conferred) is at the head of the naval
      administration of Great Britain.

Source : WordNet®

admiral
     n 1: the supreme commander of a fleet; ranks above a vice admiral
          and below a fleet admiral [syn: {full admiral}]
     2: any of several brightly colored butterflies