A bicone or dicone (Bi- comes from Latin, Di- from Greek.) is the three-dimensional geometric shape swept by revolving a rhombus around one of its axes of symmetry. Alternatively, one can view a bicone as the surface created by joining two identical right circular cones base-to-base.
A bicone can be seen as a polyhedral limiting case of an n-gonal bipyramid where n approaches infinity. It can also be seen as a dual of a cylinder as an infinite-side prism.