The Collaborative International Dictionary of English v.0.48:

Water crowfoot \Wa"ter crow"foot`\ (Bot.)
   An aquatic kind of buttercup (Ranunculus aquatilis), used
   as food for cattle in parts of England.
   [1913 Webster]

   Great water crowfoot, an American water plant (Ranunculus
      multifidus), having deep yellow flowers.
      [1913 Webster]