Arbalest

from WordNet (r) 3.0 (2006)

arbalest
    n 1: an engine that provided medieval artillery used during
         sieges; a heavy war engine for hurling large stones and
         other missiles [syn: {catapult}, {arbalest}, {arbalist},
         {ballista}, {bricole}, {mangonel}, {onager}, {trebuchet},
         {trebucket}]

from The Collaborative International Dictionary of English v.0.48

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.
   [1913 Webster] Arbalester