Flounder \Floun"der\, n. [Cf. Sw. flundra; akin to Dan. flynder, Icel. fly?ra, G. flunder, and perh. to E. flounder, v.i.] 1. (Zool.) A flatfish of the family {Pleuronectid[ae]}, of many species. [1913 Webster] 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}). [1913 Webster] 2. (Bootmaking) A tool used in crimping boot fronts. [1913 Webster]