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.
  2. Zool. The musk shrew.
  3. Zool. The desman.
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  Wa·ter rat
  1. Zool. (a) The water vole.  See under Vole.  (b) The muskrat.  (c) The beaver rat.  See under Beaver.
  2. A thief on the water; a pirate.
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  water rat
       n 1: a person who enjoys being in or on the water [syn: water
            dog]
       2: common large Eurasian vole [syn: water vole, Arvicola
          amphibius]
       3: any of various amphibious rats