n 1  :  a common Eurasian venomous snake of the genus Vipera (V. berus) that attains a length of two feet (0.6 meter), varies in color from red, brown, or gray with dark markings to black, and whose bite is usu. not fatal to humans : broadly  :  any snake of an Old World subfamily (Viperinae) of the family Viperidae  2  :  PIT VIPER  3  :  a venomous or reputedly venomous snake .
 
 
 
Similar sounding terms:  va·por  Vi·pera 
 
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