Definition of

Bipyramid

Bipyramid

A "double-pyramid", made by joining a pyramid and its mirror image base-to-base.

Here is a hexagonal bipyramid. See how the middle forms a hexagon (6-sided polygon)?

And below is a pentagonal bipyramid.

They are fun to draw, try drawing an octagonal (8-sided) bipyramid and then shade it nicely.

Bipyramid
See: Pyramid