noun
- a finishing stone of a structure.
- the crowning achievement, point, element, or event.
noun
- one of a set of slabs on the top of a wall, building, etc
- mountaineering a chockstone occurring at the top of a gully or chimney
- a crowning achievement; peakthe capstone of his career
also cap-stone, topmost stone in a construction, 1680s, from cap + stone (n.). Earliest use is figurative.