Pronunciation: (flat'fish"), [key]
—pl. (esp. collectively) -fish, (esp. referring to two or more kinds or species) -fish•es.
any fish of the order Heterosomata (Pleuronectiformes), including the halibut, sole, flounder, etc., having a greatly compressed body and swimming on one side, with both eyes on the upper side in the adult.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.