A solid figure with seven plane faces.
- ‘I'm trying to build a variety of knots and convex heptahedra with this set.’
- ‘Edges vanish, and it becomes a heptahedron, having three rhombic faces and four triangular faces.’
- ‘Around the circle - in which the heptahedron lies - another seven-fold star can be constructed.’
- ‘We are aware that the dodecahedron dissected into four congruent heptahedrons could be positioned onto the bottom of the cube.’
- ‘While all of the faces are regular and vertices equivalent, the heptahedron is self-intersecting and is therefore not considered an Archimedean solid.’
Late 17th century: from hepta- seven + -hedron, on the pattern of words such as polyhedron.