The term 'highly poisonous African snake' can be summarized by the word 'mamba', which is a five-letter word. Mambas are a group of highly venomous snakes found in Africa, with four species in the genus Dendroaspis. They are some of the fastest and most agile snakes in the world, and their venom is among the most potent of any snake. Mambas are considered to be one of the most dangerous snakes in the world, and they are responsible for many human deaths each year.