frustum

UK: /ˈfrʌstəm/ US: (frus′təm)

Inflections of 'frustum' (n):

frustums

npl

frusta

npl

WordReference Random House Unabridged Dictionary of American English © 2025

frus•tum  (frus′təm), n., pl. -tums, -ta (-tə). [Geom.]

1. Mathematics the part of a conical solid left after cutting off a top portion with a plane parallel to the base.
2. Mathematics the part of a solid, as a cone or pyramid, between two usually parallel cutting planes.

• Latin: piece, bit; probably akin to Old Irish brúid (he) breaks, Old English brȳsan to crush
• 1650–60

Collins Concise English Dictionary © HarperCollins Publishers::

frustum / ˈfrʌstəm/ noun ( -tums, -ta / -tə/)

1. the part of a solid, such as a cone or pyramid, contained between the base and a plane parallel to the base that intersects the solid
2. the part of such a solid contained between two parallel planes intersecting the solid

Etymology: 17th Century: from Latin: piece; probably related to Old English brӯsan to crush, bruise