Source : Webster's Revised Unabridged Dictionary (1913)

Madderwort \Mad"der*wort`\, n. (Bot.)
   A name proposed for any plant of the same natural order
   (Rubiace[ae]) as the madder.

Source : WordNet®

madderwort
     n : any of numerous trees or shrubs or vines of the family
         Rubiaceae [syn: {rubiaceous plant}]