Underground Story is a term used to describe a narrative that takes place in a subterranean environment. It often involves characters who are living in a hidden or secret world, and the story typically revolves around their struggles and triumphs. The term can also refer to stories that take place in caves, sewers, or other underground locations. The word 'CELLAR' is a six-letter synonym for underground story, as it is an area below ground level that is often used for storage.