flatfish

Any of the bottom-dwelling, mainly shallow-water fishes in which the adult body is strongly compressed laterally and asymmetrical, with both eyes on the same side of the head; nine families (sole, tongue-sole, plaice, halibut, dab, flounder, turbot, brill, topknot); excellent food fishes, very important commercially.

The flatfish are an order (Pleuronectiformes) of ray-finned fish, also called the Heterosomata, sometimes classified as a suborder of Perciformes. Some species face their "left" side upward, some face their "right" side upward, and others face either side upward.