Source : Webster's Revised Unabridged Dictionary (1913)

Steed \Steed\, n. [OE. stede, AS. st[=e]da a stud-horse, war
   horse, fr. st[=o]d a stud of breeding steeds; akin to G.
   stute a mare, Icel. stedda, st[=o]?, a stud. [root]163. See
   {Stud} of horses.]
   A horse, especially a spirited horse for state of war; --
   used chiefly in poetry or stately prose. ``A knight upon a
   steed.'' --Chaucer.

         Mounted upon a hot and fiery steed.      --Shak.

Source : WordNet®

steed
     n : (literary) a spirited horse for state or war