Source : Webster's Revised Unabridged Dictionary (1913)

Birthroot \Birth"root`\, n. (Bot.)
   An herbaceous plant ({Trillium erectum}), and its astringent
   rootstock, which is said to have medicinal properties.

Source : WordNet®

Trillium erectum
     n : trillium of eastern North America having malodorous pink to
         purple flowers and an astringent root used in fold
         medicine especially to ease childbirth [syn: {purple
         trillium}, {red trillium}, {birthroot}]