
en.wikipedia.org/wiki/Bipyramid
An ngonal bipyramid or dipyramid is a polyhedron formed by joining an ngonal pyramid and its mirror image basetobase. An ngonal bipyramid has 2n triangle faces, 3n edges, and 2 + n vertices.. The referenced ngon in the name of the bipyramids is not an external face but an internal one, existing on the primary symmetry plane which connects the two pyramid halves.

www.dictionary.com/browse/bipyramid
Bipyramid definition, a form symmetrical about a plane dividing it into two pyramids. See more.

www.merriamwebster.com/dictionary/bipyramid
Bipyramid definition is  a crystal consisting of two identical pyramids base to base.

math.wikia.org/wiki/Bipyramid
An ngonal bipyramid or dipyramid is a polyhedron formed by joining an ngonal pyramid and its mirror image basetobase. The referenced ngon in the name of the bipyramids is not an external face but an internal one, existing on the primary symmetry plane which connects the two pyramid halves...

www.thefreedictionary.com/bipyramid
Define bipyramid. bipyramid synonyms, bipyramid pronunciation, bipyramid translation, English dictionary definition of bipyramid. n a geometrical form consisting of two pyramids with a common polygonal base. Bipyramid  definition of bipyramid by The Free Dictionary.

encyclopedia2.thefreedictionary.com/bipyramid
An introduction of fluorine into Te[O.sub.2]based glass system results in reduction of TeOTe linkages due to a gradual transformation of trigonal bipyramid TeO4 (tbp) through TeO3+1 to trigonal pyramid TeO3 decreasing the connectivity of the tellurite glass former network.

medicaldictionary.thefreedictionary.com/bipyramidal
The newly synthesized lowdimensional network is unique in the sense that the potassium metal ion is forming seven bonds through coordination with the four sulfide ions of thiol moieties of four different thiadiazole rings, one bond with nitrogen atom of azine nitrogens and two bonds with oxygen atoms of two hydroxyl ions observing a distorted pentagonal bipyramidal geometry.

mathworld.wolfram.com/Dipyramid.html
A dipyramid, also called a bipyramid, consists of two pyramids symmetrically placed basetobase. The dipyramids are duals of the regular prisms. Their skeletons are the dipyramidal graphs. The volume of a dipyramid of halfheight h and base area A_b is equal to twice the volume of the corresponding pyramid, namely V=2/3A_bh. (1) The volume of a dipyramid whose base is a regular nsided ...

en.wikipedia.org/wiki/Triangular_dipyramid
In geometry, the triangular bipyramid (or dipyramid) is a type of hexahedron, being the first in the infinite set of facetransitive bipyramids. It is the dual of the triangular prism with 6 isosceles triangle faces.. As the name suggests, it can be constructed by joining two tetrahedra along one face. Although all its faces are congruent and the solid is facetransitive, it is not a Platonic ...

chemistry.elmhurst.edu/vchembook/220trigbipy.html
An example of trigonal bipyramid molecular geometry that results from five electron pair geometry is PCl 5. The phosphorus has 5 valence electrons and thus needs 3 more electrons to complete its octet. However this is an example where five chlorine atoms present and the octet is expanded.