noun to support and steady a stone.
2. quoin ·noun to prevent casks from rolling.
3. quoin ·noun to support the breech of a cannon.
4. quoin ·noun to wedge or lock up a form within a chase.
5. quoin ·noun a wedgelike piece of stone, wood metal, or other material, used for various purposes.
6. quoin ·noun originally, a solid exterior angle, as of a building; now, commonly, one of the selected pieces of material by which the corner is marked.