ABCDEFGHIJKLMNOPQRSTUVWXYZ Definition of Rectangular Prism more ... A solid (3-dimensional) object which has six faces that are rectangles. It has the same cross-section along a length, which makes it a prism. It is also a "cuboid". Play with one here: ../geometry/images/polyhedra.js?mode=rect-prism See: Prism Cuboids Rectangular Prisms and Cubes