portcullis (pôrtkŭlˈĭs) [key], grating or framework of strong bars of wood or iron, sharp-pointed at their lower ends, sliding vertically in the grooved jambs of a fortified portal as a protection in case of assault. First used in Roman times against Hannibal, the portcullis reached its highest development in the 12th cent. as a characteristic feature of the defensive system of a castle or fortified town. It could be dropped suddenly in a surprise attack. Through its grating the defenders could keep up a fire of arrows and other missiles. In the 14th cent., with the development of gunpowder, its tactical value was reduced.