cupola

1. (architecture) A dome-shaped ornamental structure located on top of a larger roof or dome.Examples: "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. (military, railroad) A small turret, usually on a hatch of an armoured fighting vehicle.

3. (geology) An upward-projecting mass of plutonic rock extending from a larger batholith.

4. (geometry) 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. (anatomy) A small cap over a structure that is shaped like a dome or inverted cup.Examples: "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)."

6. (railways, 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.Canadadated