(Ezekiel 4:2; 21:22) a large beam with a head of iron which was sometimes made to resemble the head of a ram. It was suspended by ropes to a beam supported by posts, and balanced so as to swing backward and forward, and was impelled by men against the wall. In attacking the walls of a fort or city, the first step appears to have been to form an inclined plane or bank of earth, comp. (Ezekiel 4:2) "cast a mount against it," by which the besiegers could bring their battering-rams and other engines to the foot of the walls, and you can find more about that here on st-takla.org on other commentaries and dictionary entries. "The battering-rams," says Mr. Layard "were of several kinds. Some were joined to movable towers which held warriors and armed men. The whole then formed one great temporary building, the top of which is represented in sculptures as on a level with the walls, and even turrets, of the besieged city. In some bas-reliefs the battering-ram is without wheels: it was then perhaps constructed upon the spot and was not intended to be moved."
Main reference: Smith's Bible Dictionary (1860s)
Bible Gallery and Bible Illustrations (thousands of images)