Flat·fish n. Zool. Any fish of the family Pleuronectidæ; esp., the winter flounder (Pleuronectes Americanus). The flatfishes have the body flattened, swim on the side, and have eyes on one side, as the flounder, turbot, and halibut. See Flounder.
n 1: sweet lean whitish flesh of any of numerous thin-bodied
fish; usually served as thin fillets
2: any of several families of fishes having flattened bodies
that swim along the sea floor on one side of the body with
both eyes on the upper side
[also: flatfishes (pl)]