Definitions of landmark
(HISTORICAL) an object that marks a boundary of land (=the limits of an area) e.g. a large stone
Some boundaries have been marked with landmarks such as stone walls or fences.
a building, structure or feature of a landscape or town that can be seen from a distance and which can be used by people to help find out where they are
Edinburgh Castle is one of the most famous landmarks in Scotland.
an event, discovery, development or change that marks an important stage in something. A landmark case is a court decision that establishes an important new legal principle or concept, or which changes the previous interpretation of current law.
The case involving Eddie Irvine was a landmark case, according to Mr Bedford's solicitor.