Common-Pool Resource
Elinor Ostrom's term for a resource where it is difficult to exclude potential users, unlike private property, but where one person's use measurably subtracts from what remains for others, unlike a non-rivalrous public good. Alpine pastures, lobster grounds, and irrigation water are all common-pool resources — which is exactly why Hardin's tragedy-of-the-commons logic applies to them in principle, even in the cases where Ostrom found it did not play out in practice.