an external solid angle of a wall or the like.

one of the stones forming it; cornerstone.

any of various bricks of standard shape for forming corners of brick walls or the like.

a wedge-shaped piece of wood, stone, or other material, used for any of various purposes.

Printing . a wedge of wood or metal for securing type in a chase.

to provide with quoins, as a corner of a wall.

to secure or raise with a quoin or wedge.

noun

angle , cornerstone , keystone , wedge