The Collaborative International Dictionary of English v.0.48:

Polygala \Po*lyg"a*la\, n. [L., milkwort, fr. Gr. ?; poly`s much
   + ? milk.]
   A genus of bitter herbs or shrubs having eight stamens and a
   two-celled ovary (as the Seneca snakeroot, the flowering
   wintergreen, etc.); milkwort.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Polygala
    n 1: type genus of the Polygalaceae: milkwort; senega; snakeroot
         [syn: Polygala, genus Polygala]