Cetacea

The order Cetacea (, L. cetus, whale) includes whales, dolphins and porpoises. Cetus is Latin and is used in biological names to mean "whale"; its original meaning, "large sea animal," was more general. It comes from Greek ketos ("sea monster"). Cetology is the branch of marine science associated with the study of cetaceans.
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Noun
1. an order of Eutheria
(synonym) order Cetacea
(hypernym) animal order
(member-holonym) Eutheria, subclass Eutheria
(member-meronym) cetacean, cetacean mammal, blower

adj. cetacean

(n. pl.)
An order of marine mammals, including the whales. Like ordinary mammals they breathe by means of lungs, and bring forth living young which they suckle for some time. The anterior limbs are changed to paddles; the tail flukes are horizontal. There are two living suborders:
  

An Order of marine mammals. The suborder Odontocetti includes dolphins, killer whales and toothed whales. Many of the great whales (such as the blue whale) belong to a different suborder (baleen whales or Mysticetti).