What is "heptahedron"

Heptahedron \Hep`ta*he"dron\, n. [Hepta- + Gr. ? seat, base, fr. ? to sit: cf. F. hepta[`e]dre.] (Geom.) A solid figure with seven sides.

n. (context mathematics English) any polyhedron having seven faces

A heptahedron (plural: heptahedra) is a polyhedron having seven sides, or faces.

A heptahedron can take a surprising number of different basic forms, or topologies. Probably most familiar are the hexagonal pyramid and the pentagonal prism. Also notable is the tetrahemihexahedron, whose seven equilateral triangle faces form a rudimentary projective plane. No heptahedra are regular.