n. 平截头体, 截头锥体

[ noun ]
a truncated cone or pyramid; the part that is left when a cone or pyramid is cut by a plane parallel to the base and the apical part is removed
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Frustum \Frus"tum\, n.; pl. L. {Frusta}, E. {Frustums}. [L.
fruslum piece, bit.]
1. (Geom.) The part of a solid next the base, formed by
cutting off the, top; or the part of any solid, as of a
cone, pyramid, etc., between two planes, which may be
either parallel or inclined to each other.

2. (Arch.) One of the drums of the shaft of a column.