D defs.my
Entry 2 senses Webster, 1913

Quoin

/(kwoin [or] koin; 277)/ · IPA /k(w)ɔɪn/
01 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.
  1. 1.
    Originally, a solid exterior angle, as of a building; now, commonly, one of the selected pieces of material by which the corner is marked.(Arch.)
  2. 2.
    A wedgelike piece of stone, wood, metal, or other material, used for various purposes;(Masonry)
Phrases & compounds
Hollow quoin — See under Hollow.
Quoin post — the post of a lock gate which abuts against the wall.