ˈ ̷ ̷ˌ ̷ ̷ noun
( -s )
Etymology: cap (I) + stone
1.
a. : a coping stone : coping
b. : the horizontal topmost stone of a dolmen
2. : the crowning point : most important element : decisive factor : climax , acme
a system of primary and secondary schools … with the university the capstone — American Guide Series: Virginia