( n. )
The portion of a vault by means of which the square space in the middle of a building is brought to an octagon or circle to receive a cupola.
( n. )
The portion of a vault by means of which the square space in the middle of a building is brought to an octagon or circle to receive a cupola.
Webster's Revised Unabridged English Dictionary. Пересмотренный полный словарь английского языка Webster. 2012