MOULDY is a term used to describe food or other items that have gone bad due to the growth of mold. FUSTY, MUSTY, and STALE are all related terms that can be used to describe the same thing. FUSTY refers to something that has a strong, unpleasant smell, MUSTY refers to something that has an old, MUSTY smell, and STALE refers to something that has lost its freshness and flavor. All three terms can be used to describe food or other items that have gone bad due to the growth of mold, which is the definition of MOULDY.