Five syllables with the second E silent and stress on the PIE is now the usual pronunciation, but six with stress on the fourth the former way of saying it, as that's closer to the Greek pronunciation of παραλληλεπίπεδον, having parallel plane surfaces -- for while the ancient Greeks may not have had algebra, they did know their geometry, including solid as well as plane figures. The επίπεδον (epipedon) part of it means plane surface, but originally meant level, and before that, level ground, which brings out that geometry literally means "measure of the earth". Note that a cube is a parallelepiped, as a square is just a special case parallelogram. Pictures, equations.
She descended the staircase wearing a crystalline parallelepiped pendant and very little else.