Source : Webster's Revised Unabridged Dictionary (1913)

Birthwort \Birth"wort`\, n.
   A genus of herbs and shrubs ({Aristolochia}), reputed to have
   medicinal properties.

Source : WordNet®

birthwort
     n : creeping plant having curving flowers thought to resemble
         fetuses; native to Europe; naturalized Great Britain and
         eastern North America [syn: {Aristolochia clematitis}]