Machicolation

A machicolation is a floor opening between the supporting corbels of a battlement, through which stones, burning objects or hot liquids (such as boiling oil or molten lead) can be dropped on attackers at the base of a defensive wall. A machicolated battlement projects outwards from the supporting wall in order to facilitate this.

The word derives from the Old French word machicoler, of unknown origins.

A variant of machicolations set in the ceiling of a passage were also colloquially known as murder-holes.