Source : Webster's Revised Unabridged Dictionary (1913)

Viper \Vi"per\, n. [F. vip[`e]re, L. vipera, probably contr. fr.
   vivipera; vivus alive + parere to bring forth, because it was
   believed to be the only serpent that brings forth living
   young. Cf. {Quick}, a., {Parent}, {Viviparous}, {Wivern},
   {Weever}.]
   1. (Zo["o]l.) Any one of numerous species of Old World
      venomous makes belonging to {Vipera}, {Clotho}, {Daboia},
      and other genera of the family {Viperid[ae]}.

            There came a viper out of the heat, and fastened on
            his hand.                             --Acts xxviii.
                                                  3.

   Note: Among the best-known species are the European adder
         ({Pelias berus}), the European asp ({Vipera aspis}),
         the African horned viper ({V. cerastes}), and the
         Indian viper ({Daboia Russellii}).

   2. A dangerous, treacherous, or malignant person.

            Who committed To such a viper his most sacred trust
            Of secrecy.                           --Milton.

   {Horned viper}. (Zo["o]l.) See {Cerastes}.

   {Red viper} (Zo["o]l.), the copperhead.

   {Viper fish} (Zo["o]l.), a small, slender, phosphorescent
      deep-sea fish ({Chauliodus Sloanii}). It has long ventral
      and dorsal fins, a large mouth, and very long, sharp
      teeth.

   {Viper's bugloss} (Bot.), a rough-leaved biennial herb
      ({Echium vulgare}) having showy purplish blue flowers. It
      is sometimes cultivated, but has become a pestilent weed
      in fields from New York to Virginia. Also called {blue
      weed}.

   {Viper's grass} (Bot.), a perennial composite herb
      ({Scorzonera Hispanica}) with narrow, entire leaves, and
      solitary heads of yellow flowers. The long, white,
      carrot-shaped roots are used for food in Spain and some
      other countries. Called also {viper grass}.

Source : WordNet®

viper's grass
     n : perennial south European herb having narrow entire leaves
         and solitary yellow flower heads and long black-skinned
         carrot-shaped edible roots [syn: {black salsify}, {scorzonera},
          {Scorzonera hispanica}]