Buckbean

from WordNet (r) 3.0 (2006)

buckbean
    n 1: perennial plant of Europe and America having racemes of
         white or purplish flowers and intensely bitter trifoliate
         leaves; often rooting at water margin and spreading across
         the surface [syn: {water shamrock}, {buckbean}, {bogbean},
         {bog myrtle}, {marsh trefoil}, {Menyanthes trifoliata}]

from The Collaborative International Dictionary of English v.0.48

buckbean \buckbean\, Buck bean \Buck" bean`\(b[=e]n`). (Bot.)
   A perennial plant ({Menyanthes trifoliata}) of Europe and
   America which grows in moist and boggy places, having racemes
   of white, reddish, or purplish flowers and intensely bitter
   trifoliate leaves, sometimes used in medicine; marsh trefoil;
   -- called also {bog bean}. It often roots at the water margin
   and spreads across the surface.

   Syn: water shamrock, bogbean, bog myrtle, marsh trefoil,
        {Menyanthes trifoliata}.
        [1913 Webster + WordNet 1.5]