In 8-dimensional geometry, the 251 honeycomb is a space-filling uniform tessellation.
It is composed of 241 polytope and 8-simplex facets arranged in an 8-demicube vertex figure.
It is created by a Wythoff construction upon a set of 9 hyperplane mirrors in 8-dimensional space.
The facet information can be extracted from its Coxeter-Dynkin diagram.
Removing the node on the short branch leaves the 8-simplex.