The Collaborative International Dictionary
Enneahedron
Enneahedria \En`ne*a*he"dri*a\, Enneahedron \En`ne*a*he"dron\, n. (Geom.) A figure having nine sides; a nonagon. [1913 Webster] ||
Wiktionary
enneahedron
n. (context geometry English) A figure with nine sides; a nonagon.
Wikipedia
Enneahedron
In geometry, a enneahedron (or nonahedron) is a polyhedron with nine faces. There are 2606 topologically distinct enneahedra and none are regular, so this name is ambiguous.