The Collaborative International Dictionary of English v.0.48:

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.
      [1913 Webster]

            A covenant never to destroy
            The earth again by flood.             --Milton.
      [1913 Webster]

   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.
      [1913 Webster]

            There is a tide in the affairs of men,
            Which, taken at the flood, leads on to fortune.
                                                  --Shak.
      [1913 Webster]

   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.
      [1913 Webster]

   4. Menstrual disharge; menses. --Harvey.
      [1913 Webster]

   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.
      [1913 Webster]

WordNet (r) 3.0 (2006):

flood tide
    n 1: the highest point of anything conceived of as growing or
         developing or unfolding; "the climax of the artist's
         career"; "in the flood tide of his success" [syn: climax,
         flood tide]
    2: the occurrence of incoming water (between a low tide and the
       following high tide); "a tide in the affairs of men which,
       taken at the flood, leads on to fortune" -Shakespeare [syn:
       flood tide, flood, rising tide] [ant: ebbtide]

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "flood tide":
   amplitude, congestion, direct tide, ebb, ebb and flow, ebb tide,
   flood, flow, flux, flux and reflux, full, full tide, fullness,
   high tide, high water, impletion, low tide, low water, lunar tide,
   neap, neap tide, opposite tide, overfullness, plenitude, plethora,
   refluence, reflux, repletion, rip, riptide, satiety, saturation,
   saturation point, solar tide, spring tide, surfeit, thalassometer,
   tidal amplitude, tidal current, tidal current chart, tidal flow,
   tidal range, tide, tide chart, tide gate, tide gauge, tide race,
   tide rip, tidewater, tideway