frus·tum /ˈfrʌstəm/
 截頭體
 Frus·tum n.; pl. L. Frusta E. Frustums
 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.
 ◄ ►
 frustum
      n : 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
      [also: frusta (pl)]