A truncated polyhedron is a polyhedron with truncated faces, given by the Schläfli symbol t
.
The operation implemented as Truncate[polyhedron, r] in the Wolfram Language
package PolyhedronOperations` displaces points along the edges of a polyhedron
by a ratio 
,
where 
is the fraction of the edge length at which to truncate, and then fills in the resulting
holes with new polygons. While this is not true truncation, the operation is equivalent
to truncation for regular solids and 
. The operation is implemented in the Wolfram
Language as TruncatedPolyhedron[poly].
-Sided
Prism." §4.2.5 in