CATAPULT

mechanism for forcefully propelling stones, spears, or other projectiles, in use since ancient times. The Romans used the word ballista to designate an engine used to hurl stones and catapulta for one that shot arrows and darts, although the larger catapults mounted a single long arm, which hurled stones and other objects. Nearly all catapults employed in ancient and medieval artillery operated by a sudden release of tension on wooden beams or twisted cords of horsehair, gut, sinew, or other fibres. An exception was the medieval trebuchet, powered by a counterweight. Modern mechanisms using hydraulic pressure, tension, or other force to launch gliders, aircraft, or missiles are also called catapults.