From Longman Dictionary of Contemporary Englishvipervi‧per /ˈvaɪpə $ -ər/ noun [countable] 1 HBAa small poisonous snake2 literary someone who behaves in an unpleasant way and harms other people
Examples from the Corpus
viper• That viper, that snake in the grass!• He was half tempted to call Penumbra himself and demand she come and collect this viper immediately.• The man who wrote the leaflet clearly thought vipers were just great.Origin viper (1500-1600) French vipère, from Latin vipera, probably from vivus “alive” + parere “to give birth to” 