Any of various marine mammals of the order Cetacea, including the whales, dolphins, and porpoises, having the general shape of a fish with forelimbs modified to form flippers, a tail with horizontal flukes, and one or two blowholes for breathing.
In some systems of classification, any of an order (Cetacea) of nearly hairless, fishlike water mammals lacking external hind limbs but having paddlelike forelimbs, including whales, porpoises, and dolphins.
Of the cetaceans.
Any of various, often very large aquatic mammals of the order Cetacea, having a hairless body that resembles that of a fish. Cetaceans have an elongated skull, a flat, horizontal tail, forelimbs modified into broad flippers, and no hind limbs. They breathe through blowholes located usually at the top of the skull. Whales, dolphins, and porpoises are cetaceans.