frustum
noun
frus·tum ˈfrə-stəm 
plural frustums or frusta ˈfrə-stə
: the basal part of a solid cone or pyramid formed by cutting off the top by a plane parallel to the base
also : the part of a solid intersected between two usually parallel planes
Example Sentences
Recent Examples on the Web The case of the 24-Seconde Architecture is shaped like a convex conical frustum. 
Carol Besler, Robb Report, 5 July 2022 The EmDrive test device used by White and his colleagues was a copper frustum—a cone with its top lopped off—that was just under a foot long. Daniel Oberhaus, Wired, 8 May 2020
Carol Besler, Robb Report, 5 July 2022 The EmDrive test device used by White and his colleagues was a copper frustum—a cone with its top lopped off—that was just under a foot long. Daniel Oberhaus, Wired, 8 May 2020 Word History
Etymology
New Latin, from Latin, piece, bit — more at bruise entry 2
First Known Use
1658, in the meaning defined above