The word pyramid means "the fire within" and refers to the cosmic energy that collects in pyramid shaped structures especially when they are aligned apropriately regarding the magnetic poles of the planet.
The Great Pyramid was originally encased with polished limestone slabs which unfortunately were removed by Egyptians for building material. Today therefore we cannot see the Great Pyramid as it was constructed-only the rough stone core.
What is the relationship between the great pyramid and the Octahedron?
The pyramid can be seen as an octahedron buried half way into the Earth. The Octahedron form is one of only 5 regular polygons possible in 3 dimensional space and thus has it's own cosmic significance irrespective of any relation with the Great Pyramid.