frustum

Noun

frustum (plural frustums or frusta)

1. A cone or pyramid whose tip has been truncated by a plane parallel to its base.
   • In a parabolic conoid this difference vaniſhes, the fruſtum being always equal to a cylinder of the ſame height upon the ſection of the conoid that biſects the altitude of the fruſtum and is parallel to its baſes.1742, Colin MacLaurin, A Treatise of Fluxions, volume 1, page 25
   • This theorem holds good for complete solids as well as frustums, whether right or oblique, and not only of the solids generated from the conic sections, but also of all pyramids, cones, and in short of any solid, whose parallel sections are similar figures.1809, William Nicholson, “FRUSTUM”, in The British Encyclopedia, or Dictionary of Arts and Sciences; […], volume III (E … I), London: Printed by C[harles] Whittingham, […]; for Longman, Hurst, Rees...
2. A portion of a sphere, or in general any solid, delimited by two parallel planes.
   • In some women it^([the os uteri]) is flat, in many more tuberose, and forming, as it were, a frustum of a sphere;[…].1840, James Blundell, Observations on Some of the More Important Diseases of Women, page 131
   • Problem 22. Determine the volume of a frustum of a sphere of diameter 49.74 cm if the diameter^([sic]) of the ends of the frustum are 24.0 and 40.0 cm, and the height of the frustum is 7.00 cm.2014, John Bird, Engineering Mathematics, page 183