cupola

noun

1. A dome-shaped ornamental structure located on top of a larger roof or dome.

   “the light falling dimly through the foggy cupola.”

   “The stations on the City & South London were small but pretty, with cupolas to accommodate the winding gear of the small and claustrophobic hydraulic lifts.”

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.

   “The cupola has a small cylindrical chimney-like bore that is lined with a refractory material.”

   “Cast iron produced in a cupola possesses the following advantages : The cost of melting is low. The control of chemical composition is better. Temperature control is easier. Molten metals can be tapped from the cupola at regular intervals.”

6. A small cap over a structure that is shaped like a dome or inverted cup.

   “the posterior cupola of the cartilaginous nasal capsule”

   “From each anterior cupola there projects forwards the processus prenasalis lateralis inferior.”

   “The cupola of the lung is mostly medial and posterior to the vein as it begins to course deeper into the thorax (Fig. 5.7).”

7. (Canada, dated)a small viewing window in the top of the caboose for looking over the train, or the part of the caboose where one looks through this window.
8. A body of members of the Sicilian Mafia who make decisions and settle disputes.