Definitionen
1.NounA projecting corner or angle; a cornerstone.
2.NounThe keystone of an arch.
3.NounA wedge used in typesetting.
4.NounA a corner of a crystal formed by the intersection of three or more faces at a point (in crystallography)
5.NounAn original angular elevation of land around which continental growth has taken place (in geology)
6.VerbTo furnish with coigns.