Noun
1. the position of a prominent or well-known object in a particular landscape;
"the church steeple provided a convenient landmark"2. an event marking a unique or important historical change of course or one on which important developments depend;
"the agreement was a watershed in the history of both nations"3. a mark showing the boundary of a piece of land
4. an anatomical structure used as a point of origin in locating other anatomical structures (as in surgery) or as point from which measurements can be taken