Crossbow

crossbow, n. a short bow fixed transversely on a stock, originally of wood then later metal, with a groove to guide the missile, or "bolt," and a trigger to release it; c. 15th century. Also arbalest. [GJ1]
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Addendum: The most important technological advance in weaponry during the European Middle Ages, the crossbow originated in Italy in the 10th century. Most fantasy gamers seem to think the appeal of the crossbow comes from being a handheld projectile weapon, like a modern gun -- but this is not the case. The crossbow was important because, unlike a regular bow, it could be pulled back with a crank; and because of this, it could be constructed of metal; and because of this, it had much greater stopping power and penetration. The crossbow was the favorite handheld ranged weapon in Europe even after the introduction of firearms, until it was finally supplanted by the harquebus in the late 1400s. [GJ1]