definition of
landmark

[1] #1 landmark n. the position of a prominent or well-known object in a particular landscape; "the church steeple provided a convenient landmark". wn

[2] #2 landmark n. [turning point, watershed] 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". wn

[3] #3 landmark n. a mark showing the boundary of a piece of land. wn

[4] #4 landmark n. 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. wn