Definitions for "onion dome"
A dome with a pointed top, its width often extending beyond the width of the tower it covers; -- a style of architecture characteristic of Russian Orthodox churches.
a pointed, bulbous dome common in Russia, Eastern European, and Islamic architecture
a dome that is shaped like a bulb; characteristic of Russian and Byzantine church architecture
Keywords:  ogee, convex, polygonal, circular, roof
A convex roof with a circular or polygonal base and an ogee-shaped section.