tidemark

noun

1. the point that something or someone has reached, receded below, or risen above: He has reached the tidemark of his prosperity.
2. a mark left by the highest or lowest point of a tide.
3. a mark made to indicate the highest or lowest point of a tide.

noun

1. a mark left by the highest or lowest point of a tide
2. a marker indicating the highest or lowest point reached by a tide
3. mainly British a mark showing a level reached by a liquida tidemark on the bath
4. informal, mainly British a dirty mark on the skin, indicating the extent to which someone has washed

1. A line or mark on a shore indicating the highest or lowest level reached by the tide.