Gaboon viperPronunciation: /gəˈbuːn/Definition of Gaboon viper noun a large, thick-bodied venomous African snake with a pair of horn-like scales on the snout, having a body richly patterned with brown, purple, and cream. Bitis gabonica, family Viperidae Origin: early 20th century: named after Gaboon (now Gabon)Gaboon viper in other Oxford dictionaries Definition of Gaboon viper in the US English dictionary