any of several extremely venomous snakes of the viper family (Viperidae) found in diverse habitats from cultivated lands to forests throughout tropical America and tropical Asia. The fer-de-lance, known in Spanish as barba amarilla (“yellow chin”), is a pit viper (subfamily Crotalinae)—i.e., distinguished by a small sensory pit between each eye and nostril. It has a broad triangular head and is usually about 1.2 to 2 metres (4 to 7 feet) long. It is gray or brown, marked by a series of black-edged diamonds often bordered in a lighter colour. Its bite can be fatal to humans.