Source : Webster's Revised Unabridged Dictionary (1913)

Cetacea \Ce*ta"ce*a\, n. pl. [NL., from L. cetus whale, Gr. ?.]
   (Zo["o]l.)
   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:
   (a) The {Mysticete} or whalebone whales, having no true teeth
       after birth, but with a series of plates of whalebone
       [see {Baleen}.] hanging down from the upper jaw on each
       side, thus making a strainer, through which they receive
       the small animals upon which they feed.
   (b) The {Denticete}, including the dolphins and sperm whale,
       which have teeth. Another suborder ({Zeuglodontia}) is
       extinct. The {Sirenia} were formerly included in the
       Cetacea, but are now made a separate order.

Source : WordNet®

Cetacea
     n : an order of Eutheria [syn: {order Cetacea}]