Small retrosnub disoctahedron

The small retrosnub disoctahedron, sirsido, or compound of two great icosahedra is a uniform polyhedron compound. It consists of 40 triangles (8 pairs of which form hexagrams due to following in the same plane), with five faces joining at a vertex.

It can be constructed from the pentagrammatic snub pseudodisoctahedron by replacing each small stellated dodecahedron with the great icosahedron with which it shares its edges.

Its quotient prismatic equivalent is the pyritohedral great icosahedral antiprism, which is four-dimensional.