In graph theory, the Cartesian product G □ H of graphs G and H is a graph such that: the vertex set of G □ H is the Cartesian product V × V; and two vertices and are adjacent in G □ H if and only if either u = v and u' is adjacent to v' in H, or u' = v' and u is adjacent to v in G.The Cartesian product of graphs is sometimes called the box product of graphs [Harary 1969]. Wikipedia