What is "flood mark"

Flood \Flood\ (fl[u^]d), n. [OE. flod a flowing, stream, flood, AS. fl[=o]d; akin to D. vloed, OS. fl[=o]d, OHG. fluot, G. flut, Icel. fl[=o][eth], Sw. & Dan. flod, Goth. fl[=o]dus; from the root of E. flow. [root]80. See Flow, v. i.]

1. A great flow of water; a body of moving water; the flowing stream, as of a river; especially, a body of water, rising, swelling, and overflowing land not usually thus covered; a deluge; a freshet; an inundation.

   A covenant never to destroy The earth again by flood.
   --Milton.

2. The flowing in of the tide; the semidiurnal swell or rise of water in the ocean; -- opposed to ebb; as, young flood; high flood.

   There is a tide in the affairs of men, Which, taken at the flood, leads on to fortune.
   --Shak.

3. A great flow or stream of any fluid substance; as, a flood of light; a flood of lava; hence, a great quantity widely diffused; an overflowing; a superabundance; as, a flood of bank notes; a flood of paper currency.

4. Menstrual disharge; menses.
   --Harvey.

   Flood anchor (Naut.), the anchor by which a ship is held while the tide is rising.

   Flood fence, a fence so secured that it will not be swept away by a flood.

   Flood gate, a gate for shutting out, admitting, or releasing, a body of water; a tide gate.

   Flood mark, the mark or line to which the tide, or a flood, rises; high-water mark.

   Flood tide, the rising tide; -- opposed to ebb tide.

   The Flood, the deluge in the days of Noah.