trebuchet

Trebuchet, treb′ū-shet, n. a military engine like the ballista.

To these engines the besieged opposed the first trebuchet, and another mounted in the barbican.

Such was the principle of the "trebuchet," the enormous engines which carried devastation and destruction to medieval castles.

Conversely, we might describe a staff-sling as a hand-trebuchet.

The medival trebuchet was a sling wielded by a gigantic arm of wood.