Source : Webster's Revised Unabridged Dictionary (1913)

Flounder \Floun"der\, n. [Cf. Sw. flundra; akin to Dan. flynder,
   Icel. fly?ra, G. flunder, and perh. to E. flounder, v.i.]
   1. (Zo["o]l.) A flatfish of the family {Pleuronectid[ae]}, of
      many species.

   Note: The common English flounder is {Pleuronectes flesus}.
         There are several common American species used as food;
         as the smooth flounder ({P. glabra}); the rough or
         winter flounder ({P. Americanus}); the summer flounder,
         or plaice ({Paralichthys dentatus}), Atlantic coast;
         and the starry flounder ({Pleuronectes stellatus}).

   2. (Bootmaking) A tool used in crimping boot fronts.

Flounder \Floun"der\, v. i. [imp. & p. p. {Floundered}; p. pr. &
   vb. n. {Floundering}.] [Cf. D. flodderen to flap, splash
   through mire, E. flounce, v.i., and flounder the fish.]
   To fling the limbs and body, as in making efforts to move; to
   struggle, as a horse in the mire, or as a fish on land; to
   roll, toss, and tumble; to flounce.

         They have floundered on from blunder to blunder. --Sir
                                                  W. Hamilton.

Flounder \Floun"der\, n.
   The act of floundering.

Source : WordNet®

flounder
     n 1: flesh of any of various American and European flatfish
     2: any of various European and non-European marine flatfish
     v 1: walk with great difficulty; "He staggered along in the heavy
          snow" [syn: {stagger}]
     2: behave awkwardly; have difficulties; "She is floundering in
        college"