Definition of: frustum

(frus′təm) noun plural ·tums or ·ta (-tə)
1. Geom. a That which is left of a solid after cutting off the upper part: said of a cone or a pyramid. b That part of a solid included between any two planes, or, in the case of a sphere, that part between two parallel planes.
2. Archit. A fragment; a broken shaft of a column. [<L, fragment]