Definition of quoin

• n. - Originally, a solid exterior angle, as of a building; now, commonly, one of the selected pieces of material by which the corner is marked.
• n. - A wedgelike piece of stone, wood metal, or other material, used for various purposes
• n. - to support and steady a stone.
• n. - To support the breech of a cannon.
• n. - To wedge or lock up a form within a chase.
• n. - To prevent casks from rolling.