water rat

from WordNet (r) 3.0 (2006)

water rat
    n 1: a person who enjoys being in or on the water [syn: {water
         dog}, {water rat}]
    2: common large Eurasian vole [syn: {water vole}, {water rat},
       {Arvicola amphibius}]
    3: any of various amphibious rats

from The Collaborative International Dictionary of English v.0.48

Muskrat \Musk"rat`\, n.
   1. (Zool.) A North American aquatic fur-bearing rodent
      ({Ondatra zibethica} formerly {Fiber zibethicus}). It
      resembles a rat in color and having a long scaly tail, but
      the tail is compressed, the hind feet are webbed, and the
      ears are concealed in the fur. It has scent glands which
      secrete a substance having a strong odor of musk. Called
      also {musquash}, {musk beaver}, {ondatra}, and sometimes
      {water rat}.
      [1913 Webster +PJC]

   2. (Zool.) The musk shrew.
      [1913 Webster]

   3. (Zool.) The desman.
      [1913 Webster]

from The Collaborative International Dictionary of English v.0.48

Water rat \Wa"ter rat`\
   1. (Zool.)
      (a) The water vole. See under {Vole}.
      (b) The muskrat.
      (c) The beaver rat. See under {Beaver}.
          [1913 Webster]

   2. A thief on the water; a pirate.
      [1913 Webster]