So you know that the dipyramid is a double pyramid, and you can guess that a square dipyramid is a double square pyramid (with four triangular faces and a square basis, like the Egyptian pyramids). Now all you need is to know what gyroelongated means. It means that the polyhedron has been elongated by  placing an antiprism in the middle of the polyhedron. An antiprism is a shape whose bases are identical in shape and connected by a band of triangles. In short, we have a bottom pyramid and a top pyramid, with a band of triangles connected the two.