Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. In geometry, the gyroelongated square bipyramid is one of the Johnson solids (J17). As the name suggests, it can be constructed by gyroelongating an octahedron by inserting a square antiprism between its congruent halves. It is a deltahedron. The 92 Johnson solids were named and described by Norman Johnson in 1966. In geometry, an octahedron (plural: octahedra) is a polyhedron with eight faces. A regular octahedron is a Platonic solid composed of eight equilateral triangles, four of which meet at each vertex.