water vole

from WordNet (r) 3.0 (2006)

water vole
    n 1: common large Eurasian vole [syn: {water vole}, {water rat},
         {Arvicola amphibius}]
    2: of western North America [syn: {water vole}, {Richardson
       vole}, {Microtus richardsoni}]

from The Collaborative International Dictionary of English v.0.48

Water vole \Wa"ter vole`\ (Zool.)
   See under {Vole}.
   [1913 Webster]