The term 'Largest Toad' is referring to the Giant Toad, also known as the Marine Toad or Cane Toad. It is native to Central and South America and is the largest species of toad in the world, reaching up to 9 inches in length. The crossword solution for this term is AGUA, which is the Spanish word for water. This is fitting as the Giant Toad is an aquatic species that lives in and around bodies of water.