Source : Webster's Revised Unabridged Dictionary (1913)

Milkwort \Milk"wort`\, n. (Bot.)
   A genus of plants ({Polygala}) of many species. The common
   European {P. vulgaris} was supposed to have the power of
   producing a flow of milk in nurses.

   Note: The species of {Campanula}, or bellflower, are
         sometimes called milkwort, from their juice.

Source : WordNet®

milkwort
     n : any of various plants of the genus Polygala