porpoise

from WordNet (r) 3.0 (2006)

porpoise
    n 1: any of several small gregarious cetacean mammals having a
         blunt snout and many teeth

from The Collaborative International Dictionary of English v.0.48

Porpoise \Por"poise\, n. [OE. porpeys, OF. porpeis, literally,
   hog fish, from L. porcus swine + piscis fish. See {Pork}, and
   {Fish}.]
   1. (Zool.) Any small cetacean of the genus {Phoc[ae]na},
      especially {Phoc[ae]na communis}, or {Phoc[ae]na
      phoc[ae]na}, of Europe, and the closely allied American
      species ({Phoc[ae]na Americana}). The color is dusky or
      blackish above, paler beneath. They are closely allied to
      the dolphins, but have a shorter snout. Called also
      {harbor porpoise}, {herring hag}, {puffing pig}, and
      {snuffer}.
      [1913 Webster]

   2. (Zool.) A true dolphin ({Delphinus}); -- often so called
      by sailors.
      [1913 Webster]

   {Skunk porpoise}, or {Bay porpoise} (Zool.), a North American
      porpoise ({Lagenorhynchus acutus}), larger than the common
      species, and with broad stripes of white and yellow on the
      sides. See Illustration in Appendix.
      [1913 Webster]

from Moby Thesaurus II by Grady Ward, 1.0

30 Moby Thesaurus words for "porpoise":
      Loch Ness monster, alevin, benthon, benthos, cetacean, dolphin,
      fingerling, fish, fry, game fish, grilse, kipper, man-eater,
      man-eating shark, marine animal, minnow, minny, nekton, panfish,
      plankton, salmon, sea monster, sea pig, sea serpent, sea snake,
      shark, smolt, sponge, tropical fish, whale