Piles or Stacks is a term used to describe a large number of items that are placed in a pile or stack. HEAPS is a synonym for this term, which is defined as a large number of items that are piled up or stacked together. This term is often used to describe a large amount of something, such as a large pile of leaves or a stack of books. It can also be used to describe a large group of people or objects that are gathered together.