The Collaborative International Dictionary of English v.0.48:

viper \vi"per\ (v[imac]"p[~e]r), 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.]
   [1913 Webster]
   1. (Zool.) Any one of numerous species of Old World venomous
      snakes belonging to Vipera, Clotho, Daboia, and
      other genera of the family Viperidae.
      [1913 Webster]

            There came a viper out of the heat, and fastened on
            his hand.                             --Acts xxviii.
                                                  3.
      [1913 Webster]

   Note: Among the best-known species are the European adder
         (Pelias berus), the European asp (Vipera aspis),
         the African horned viper (Vipera cerastes), and the
         Indian viper (Daboia Russellii).
         [1913 Webster]

   2. A dangerous, treacherous, or malignant person.
      [1913 Webster]

            Who committed
            To such a viper his most sacred trust
            Of secrecy.                           --Milton.
      [1913 Webster]

   3. Loosely, any venomous or presumed venomous snake.
      [PJC]

   Horned viper. (Zool.) See Cerastes.

   Red viper (Zool.), the copperhead.

   Viper fish (Zool.), 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.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Asp \Asp\ ([.a]sp), n. [L. aspis, fr. Gr. 'aspi`s: cf. OF. aspe,
   F. aspic.] (Zool.)
   A small, hooded, poisonous serpent of Egypt and adjacent
   countries, whose bite is often fatal. It is the Naja haje.
   The name is also applied to other poisonous serpents, esp. to
   Vipera aspis of southern Europe. See Haje.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Vipera aspis
    n 1: of southern Europe; similar to but smaller than the adder
         [syn: asp, asp viper, Vipera aspis]