any member of the group of marine mammals that includes whales, dolphins and porpoises
Cetaceans are animals such as whales, dolphins, and porpoises. a mammal that lives in the sea, such as a whale (cetus , from ketos). Any of the exclusively aquatic placental mammals constituting the order Cetacea. They are found in oceans worldwide and in some freshwater environments. Modern cetaceans are grouped in two suborders: about 70 species of toothed whales (Odontoceti) and 13 species of toothless baleen whales (Mysticeti). They have a tapered body, no external hind limbs, and a tail ending in a horizontal blade of two lobes, or flukes. Cetaceans must come to the water's surface to breathe through blowholes located on top of their head. See also whale
More generally, relating to large aquatic mammals, either directly or by analogy
An animal belonging to the order Cetacea, including dolphins, porpoises, and whales
large aquatic carnivorous mammal with fin-like forelimbs no hind limbs, including: whales; dolphins; porpoises; narwhals of or relating to whales and dolphins etc