The removal of portions of Solids falling outside a set of symmetrically placed planes. The five Platonic Solids belong to one of the following three truncation series (which, in the first two cases, carry the solid to its Dual Polyhedron).
See also Stellation, Truncated Cube, Truncated Dodecahedron, Truncated Icosahedron, Truncated Octahedron, Truncated Tetrahedron, Vertex Figure