The term 'Underground Store' can be summarized as a store located in a CELLAR, which is a room or storage space below ground level. The word 'CELLAR' is a six-letter word that is often used to describe an underground store. This type of store is typically used to store food and other items that need to be kept cool or away from the elements. It is also sometimes used as a place to store wine and other alcoholic beverages.