(graph theory) An unsolved problem in mathematics, asking for the largest possible number of edges in a bipartite graph that has a given number of vertices and has no complete bipartite subgraphs of a given size.

(graph theory) The function for which the Zarankiewicz problem seeks a formula: z(m, n; s, t), denoting the largest possible number of edges in a bipartite graph G = (U, V, E) for which |U| = m and |V| = n, but which does not contain a subgraph of the form K_(s,t).