Any one of various species of small carnivores belonging to
   the genus Putorius, as the ermine and ferret. They have a slender,
   elongated body, and are noted for the quickness of their movements and
   for their bloodthirsty habit in destroying poultry, rats, etc. The
   ermine and some other species are brown in summer, and turn white in
   winter; others are brown at all seasons.