Triangular retroprism

The triangular retroprism, also called the triangular crossed antiprism, is a prismatic isogonal polyhedron. It consists of 2 base triangles and 6 side triangles. The side triangles are isosceles triangles. Each vertex joins one base triangle and three side triangles. It is a crossed antiprism based on a triangle, seen as a 3/2-gon rather than 3/1.

If tried to make uniform, the height becomes zero and all of the triangles coincide, so it can be thought of as a degenerate uniform polyhedron.

It is isomorphic to the octahedron.