cupola

Etymology

Borrowed from Italian cupola, from Latin cūpula (“little tub”); from Latin cūpa, cuppa (“cup”); named for its resemblance to a cup turned over.

noun

1. (architecture) A dome-shaped ornamental structure located on top of a larger roof or dome.
   the light falling dimly through the foggy cupola. 1886, Robert Louis Stephenson, The Strange Case of Dr Jekyll and Mr Hyde
   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. 2012, Andrew Martin, Underground Overground: A passenger's history of the Tube, Profile Books, page 101
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. A type of furnace used for smelting.
   The cupola has a small cylindrical chimney-like bore that is lined with a refractory material. 2008, Matthew Stein, When Technology Fails
   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. 2009, S.K. Garg, Comprehensive Workshop Technology, page 260
6. (anatomy) 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. 1937, Sir Gavin De Beer, The Development of the Vertebrate Skull, page 180
   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). 2015, Charles E. Smith, Trauma Anesthesia, page 85
7. (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.