Cupola

Noun

1. A dome-shaped ornamental structure located on top of a larger roof or dome.
2. A small turret, usually on a hatch of an armoured fighting vehicle.
3. An upward-projecting mass of plutonic rock extending from a larger batholith.
4. A solid formed by joining two polygons, one (the base) with twice as many edges as the other, by an alternating band of isosceles triangles and rectangles.
5. A type of furnace used for smelting.