Cancavity has a simple definition, its measure is: area of the region divided by the area of its convex hull. Most concave is value nearest to zero. You can't just make up definitions.
Well, actually the point of definitions is that you can just make them up, but if you're using a non-standard one you really need to say so. I do find the definition in the article pretty pointless (aside from the fact that it has way too many points).
