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.]
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.
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.
To such a viper his most sacred trust
Of secrecy. --Milton.
3. Loosely, any venomous or presumed venomous snake.
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
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
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.