Definition of Landmark

Noun: landmark 'land,maa(r)k

The position of a prominent or well-known object in a particular landscape
"the church steeple provided a convenient landmark"
An event marking a unique or important historical change of course or one on which important developments depend
"the agreement was a landmark in the history of both nations";
- turning point, watershed, cusp
A mark showing the boundary of a piece of land
(surgery) 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