/flat"fish'/ , n. , pl. ( esp. collectively ) flatfish , ( esp. referring to two or more kinds or species ) flatfishes .
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.
[ 1700-10; FLAT 1 + FISH ]