Triangular bipyramid

Two tetrahedra joined by one face

In geometry, the triangular bipyramid is the hexahedron with six triangular faces, constructed by attaching two tetrahedra face-to-face. The same shape is also called the triangular dipyramid or trigonal bipyramid. If these tetrahedra are regular, all faces of triangular bipyramid are equilateral. It is an example of a deltahedron, composite polyhedron, and Johnson solid.

This keyword could refer to multiple things. Here are some suggestions: