0 a mark that shows the highest level that the sea or river reaches at a particular place
1 the most successful point of something:
When do they anticipate that the high water mark of their demands will be reached?
This month should have been in a real sense the high water mark of the motorway system.
It will draw the high water mark at a level below which we shall not be able to argue.
The controlled waters for dumping purposes will be regarded as bounded on the landward side by high water mark.
Of course, 27 members may not be the high water mark of enlargement.
In some cases the international boundary is on the high water mark on the other side of the inlet.
We all know what the ordinary high water mark of an ordinary tide is; but who is to say what the ordinary spring tide is?
It was not by any means the high water mark of our demands here for 40 or 50 years.
