In geometry, a birotunda is any member of a family of dihedral-symmetric Polyhedra, formed from two rotunda adjoined through the largest face. They are similar to a bicupola but instead of alternating squares and triangles, it alternates pentagons and triangles around an axis.
The image below shows a pentagonal gyrobirotunda divided to show the two pentagonal rotunda from which it is made

If both rotunda are aligned as mirror images they form a pentagonal orthobirotunda, pictured below.