Source : Webster's Revised Unabridged Dictionary (1913)

Longbow \Long"bow`\, n.
   The ordinary bow, not mounted on a stock; -- so called in
   distinction from the crossbow when both were used as weapons
   of war. Also, sometimes, such a bow of about the height of a
   man, as distinguished from a much shorter one.

   {To draw the longbow}, to tell large stories.

Source : WordNet®

longbow
     n : a powerful wooden bow drawn by hand; usually 5-6 feet long;
         used in medieval England