nounpl. (see fish) -·fish·, -·fish·es
any of an order (Pleuronectiformes) of marine bony fishes, including flounders and soles, having a laterally flattened, asymmetrical body with, as an adult, both the eyes and the mouth on the upper side
nounpl. flatfish, or flat·fish·es
Any of numerous chiefly marine fishes of the order Pleuronectiformes, including the flounders, soles, and halibuts, having a laterally compressed body with both eyes on the upper side.
(plural flatfish or flatfishes)