Etymology From Middle English capston; equivalent to cap + stone.
1
Any of the stones making up the top layer of a wall; a coping stone.
2
Figuratively A crowning achievement, culmination or finishing touch.
“You see, I’ve never had a girl friend,” I added, by way of topping the obelisk of silliness with the capstone of fatuity.1904, Guy Wetmore Carryl, Far from the Maddening Girls, chapter 5:
Success of the Apollo program has been the capstone to a series of significant accomplishments for the United States in space in a broad spectrum of manned and unmanned exploration missions and in the application of space techniques for the benefit of man.1969, The Post-Apollo Space Program: Directions for the Future, NASA:
Etymology From Middle English capston; equivalent to cap + stone.
1
To complete as a crowning achievement; to top off.
Capstoning a decade's worth of linked short stories, The Quiet War (2008) was a vivid and tense novel about a solar system sliding into conflict.2012, Keith Brooke, Strange Divisions and Alien Territories, page 23:
“Capstoned” units are now able to train and plan in peacetime with the command with which they will fight in wartime.1981, Army Reserve Magazine, volumes 27-28, page 24: