copestone

UK: /ˈkəʊpˌstəʊn/ US: (kōp′stōn′)

WordReference Random House Unabridged Dictionary of American English © 2025

cope•stone  (kōp′stōn′), n. 

1. Building the top stone of a building or other structure.
2. Building a stone used for or in coping.
3. Building the crown or completion;
   finishing touch.

• cope² + stone 1560–70

Collins Concise English Dictionary © HarperCollins Publishers::

copestone / ˈkəʊpˌstəʊn/ noun

1. Also called: coping stone a stone used to form a coping
2. Also called: capstone the stone at the top of a building, wall, etc

WordReference Random House Learner's Dictionary of American English © 2025

cap•stone /ˈkæpˌstoʊn/   n. [countable]

1. Building, Architecture a finishing stone of a structure.
2. the most glorious and usually final achievement:
   The Nobel prize was the capstone of his long career.

WordReference Random House Unabridged Dictionary of American English © 2025

cap•stone  (kap′stōn′), n. 

1. Building, Architecture a finishing stone of a structure.
2. the crowning achievement, point, element, or event.

• Middle English. See cap¹, stone 1350–1400

Collins Concise English Dictionary © HarperCollins Publishers::

capstone / ˈkæpˌstəʊn/, copestone / ˈkəʊpˌstəʊn/ noun

1. one of a set of slabs on the top of a wall, building, etc