Ot·ter n.
 1. Zool. Any carnivorous animal of the genera Lutra, Enhydra, and related genera of the family Mustelidae.  Several species are described.  They have large, flattish heads, short ears, and webbed toes.  They are aquatic, and feed on fish.  The sea otter (Enhydra lutris) also eats clams, crabs, starfish, abalone, and other marine animals; they may come to the surface, and lying on their backs using the stomach as a table, may be seen cracking open the shell of its prey with a rock.  The common otter of Europe is Lutra vulgaris; the North American otter (or American otter) is Lutra Canadensis, which inhabits marshes, streams and rivers; other species inhabit South America and Asia.  The North American otter adult is about three to four feet long (including the tail) and weighs from 10 to 30 pounds; the sea otter is commonly four feet long and 45 pounds (female) or 60 pounds (male).  Their fur is soft and valuable, and in the nineteenth century they were hunted extensively.  The sea otter was hunted to near extinction by 1900, and is now protected.  Fewer than 3,000 sea otters are believed to live along the central California coast.
 2. Zool. The larva of the ghost moth. It is very injurious to hop vines.
 Otter hound, Otter dog Zool., a small breed of hounds, used in England for hunting otters; see otterhound .
 Otter sheep. See Ancon sheep, under Ancon.
 Otter shell Zool., very large bivalve mollusk (Schizothaerus Nuttallii) found on the northwest coast of America.  It is excellent food, and is extensively used by the Indians.
 Sea otter. Zool. See in the Vocabulary.