It is a measure of number of bounded faces of a graph -https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwie4YqUupj2AhXlT2wGHbFfB_8QFnoECB0QAQ&url=https%3A%2F%2Ftransportist.org%2F2016%2F11%2F14%2Felements-of-access-meshedness%2F&usg=AOvVaw36tX5ylPYFGELpemfYcEuF