- any of various slender, air-breathing fishes of the order (or subclass) Dipnoi, of rivers and lakes in Africa, South America, and Australia, having a lunglike air bladder as well as gills and growing to a length of 3 to 6 feet (0.9 to 1.8 meters).
- any freshwater bony fish of the subclass Dipnoi, having an air-breathing lung, fleshy paired fins, and an elongated body. The only living species are those of the genera Lepidosiren of South America, Protopterus of Africa, and Neoceratodus of Australia
