The term 'AT MAD' can be solved by the six-letter word 'REISER'. This is a German word meaning 'JOURNEY' or 'TRAVEL'. It is derived from the Latin word 'reis', which means 'to go'. The term 'AT MAD' is an abbreviation for 'Atlas of Madagascan Flora and Fauna', which is a book published in 2019. It is a comprehensive guide to the plants and animals of Madagascar, and it includes detailed descriptions of the species, their habitats, and their distributions.