coign

noun

1. A projecting corner or angle; a cornerstone.

   “By many a dern and painful perch Of Pericles the careful search By the four opposing coigns Which the world together joins, Is made with all due diligence”

   “Kind air defined the coigns of houses in Kildare street.”

   “this snug monastic coign, this dreamy and heatless alcove of what we call the best of thought.”

   “They lay quietly as the morning advanced its little way, hid snug in their greenwood coign. —”

   “The wall was intricately labored—lined and coigned and serried with regular and irregular groups of windows, balconies, buttresses ...”

2. The keystone of an arch.
3. A wedge used in typesetting.
4. A a corner of a crystal formed by the intersection of three or more faces at a point (in crystallography)

   “In both the orthogonal and clinographic projections the light rays joining the eye and crystal coigns (solid angles, corners at which three or more edges meet) are all parallel”

   “Axes taken from corner to corner ( coign to coign is the correct terminology ) in a cube are such …”

5. An original angular elevation of land around which continental growth has taken place (in geology)

   “South of the North American coign we have again a pair of east - west mountain chains”

verb

1. (transitive)To furnish with coigns.

   “The angles were always coigned, and the arches turned with squared stone, brought from Caen in Normandy […]”