noun. A polyhedron, such as a cube, that has six faces.

noun. A solid body having six faces; especially, the regular hexahedron or cube. Also hexaëdron.

noun. A solid body of six sides or faces.

noun. a hexagon having six equal squares for its sides; a cube.

noun. A polyhedron with six faces; the regular hexahedron is more commonly called the cube and is one of the Platonic solids.

noun. any polyhedron having six plane faces

"Plato, the dialectician, condescended to allow to God the liberty of making five worlds; because, said he, there are five regular solids in geometry, the tetrahedron, the cube, the hexahedron, the dodecahedron, and the icosahedron."

hexahedral  

polyhedron  

rhombohedron