[quoin] n [alter. of [1]coin] (1532) 1 a: a solid exterior angle (as of a building) b: one of the members (as a block) forming a quoin and usu. differentiated from the adjoining walls by material, texture, color, size, or projection
2: the keystone or a voussoir of an arch
3: a wooden or expandable metal block used by printers to lock up a form within a chase
[2]quoin vt (1683) 1: to equip (a type form) with quoins
2: to provide with quoins "~ed walls"