The Collaborative International Dictionary of English v.0.48:

Madnep \Mad"nep\, n.
   1. (Bot.) The masterwort (Peucedanum Ostruthium), a tall
      and coarse European umbelliferous plant.
      [1913 Webster]

   2. (Bot.) A biennial weed in Europe and America having large
      pinnate leaves and yellow flowers and a bitter and
      somewhat poisonous root; the ancestor of cultivated
      parsnip; called also wild parsnip.
      [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Masterwort \Mas"ter*wort`\, n. (Bot.)
   (a) A tall and coarse European umbelliferous plant
       (Peucedanum Ostruthium, formerly Imperatoria).
   (b) The Astrantia major, a European umbelliferous plant
       with a showy colored involucre.
   (c) Improperly, the cow parsnip (Heracleum lanatum).
       [1913 Webster]