vi·per n.
  1. Zool. Any one of numerous species of Old World venomous snakes belonging to Vipera, Clotho, Daboia, and other genera of the family Viperidae.
     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 (Vipera 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. 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.
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  Bu·gloss n.; pl. Buglosses   Bot. A plant of the genus Anchusa, and especially the Anchusa officinalis, sometimes called alkanet; oxtongue.
  Small wild bugloss, the Asperugo procumbens and the Lycopsis arvensis.
  Viper's bugloss, a species of Echium.
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  viper's bugloss
       n : a coarse prickly European weed with spikes of blue flowers;
           naturalized in United States [syn: blueweed, blue
           devil, blue thistle, Echium vulgare]