D defs.my
Entry 2 senses Webster, 1913

Tidemark

· Tide·mark · IPA
01 n. a mark on a shore line indicating the normal level of the water at high tide, caused by the action of the flowing water; sometimes also use…
  1. 1.
    a mark on a shore line indicating the normal level of the water at high tide, caused by the action of the flowing water; sometimes also used for the mark left at the point of the normal low tide; -- called also high water mark. Also: high water mark
  2. 2.
    the maximum level which some activity has reached and from which it has declined; -- called also high water mark.[fig.] Also: high water mark