The term shield cut, as suggested by Tillander, indicates all historical triangular cuts. The basic blueprint comes from half an octahedron.
When an octahedron is cleaved through the middle, each half forms a stone with a large, flat bottom and a triangular top with slightly sloping sides. When the stone is mounted with the triangle facing up the stone resembles the shape of a shield; one of the most prevalent emblems of heraldry and warfare.
Shield-Shaped Diamond Earrings.
Shield-Shaped Intense Fancy Yellow Diamond, Platinum, and Diamond Cocktail Ring.