machicolation

machicolation is a Noun

Definition:

[1] An opening between the corbels which support a projecting parapet, or in the floor of a gallery or the roof of a portal, shooting or dropping missiles upen assailants attacking the base of the walls. Also, the construction of such defenses, in general, when of this character. See Illusts. of Battlement and Castle.

[2] The act of discharging missiles or pouring burning or melted substances upon assailants through such apertures.