Definition of "quoin"

quoin

/k(w)ɔɪn/

noun
plural quoins
1. Any of the corner building blocks of a building, usually larger or more ornate than the surrounding blocks.
  Quotations
  In Casterbridge there stood a noble pile, […] But evil days beset that domicile;The stately beauties of its roof and wallPassed into sordid hands. Condemned to fallWere cornice, quoin, and cove,And all that art had wove in antique style.
  1901, Thomas Hardy, A Man (In Memory Of H. Of M.)
2. The keystone of an arch.
3. (printing, historical) A metal wedge which fits into the space between the type and the edge of a chase, and is tightened to fix the metal type in place.
  Quotations
  Next fit the quoins, using the “persuader” to squeeze in the pages, and tap up all around.
  1898, John Southward, Modern Printing: A Handbook of the Principles and Practice of Typography and the Auxiliary Arts
4. (obsolete, nautical) A form of wedge used to prevent casks from moving
5. (firearms) A wedge of wood or iron put under the breech of heavy guns or the muzzle of siege-mortars to raise them to the proper level.
6. (horticulture) A number of apple varieties with a distinctive ribbed appearance, like corners of a coin.
verb
third-person singular simple present quoins, present participle quoining, simple past and past participle quoined
1. (transitive) To wedge or steady with quoins.