in Mathematics, a part of some solid body separated from the rest.

The frustum of a cone is the part that remains, when the top is cut off by a plane parallel to the base; and is otherwise called a truncated cone. See Conic Sections.

The frustum of a pyramid is also what remains after the top is cut off by a plane parallel to its base.

The frustum of a globe or sphere is any part thereof cut off by a plane, the solid contents of which may be found by this rule: To three times the square of the semidiameter of the base add the square of its height; then multiply that sum by the height, and this product multiplied by .5236 gives the solidity of the frustum.