Definition for our world:
Literally: a weapon for performing a siege. One ancient strategy for combat was a patience game. One group of people would build a strong fortification, then hide within it when adversaries came. The adversaries would surround the fortification (lay siege to it), then attempt to coax those within the fortification out or somehow break in. Siege weapons were designed to break down the walls of a fortification, or to defend a fortification from those seeking to break in.