![A solid cone with its top missing. The newly cut face and the base are parallel.](/glossary/frustum-of-a-cone/images/frustum-of-a-cone.png)
A frustum of a cone is the shape that is left when a cone has its top sliced off (and discarded) along a plane parallel to its base.
A frustum of a cone is the shape that is left when a cone has its top sliced off (and discarded) along a plane parallel to its base.