Source : Webster's Revised Unabridged Dictionary (1913)

Arbalest \Ar"ba*lest\, Arbalist \Ar"ba*list\, n. [OF. arbaleste,
   LL. arbalista, for L. arcuballista; arcus bow + ballista a
   military engine. See {Ballista}.] (Antiq.)
   A crossbow, consisting of a steel bow set in a shaft of wood,
   furnished with a string and a trigger, and a mechanical
   device for bending the bow. It served to throw arrows, darts,
   bullets, etc. [Written also {arbalet} and {arblast}.]
   --Fosbroke.

Source : WordNet®

arbalest
     n : medieval artillery used during sieges; a heavy war engine
         for hurling large stones and other missiles [syn: {catapult},
          {arbalist}, {ballista}, {bricole}, {mangonel}, {onager},
          {trebuchet}, {trebucket}]