Dictionary.net

• 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

2006 - WordNet 3.0
By Princeton University

• 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

2011 - English Dictionary Database
By DataStellar Co., Ltd