The word "stack" refers to a pile of things placed on top of one another. There are a lot of synonyms for the word "stack" like heap, pile, mound, collection, and batch. The term "heap" describes a disorganized stack of things, whereas a "pile" often refers to a neat and systematic arrangement of things. "Mound" is another term used for a pile, but it usually pertains to a large heap of dirt or stones. The word "collection" can be used to refer to a stack of objects with common characteristics, and "batch" is used to describe a particular amount of products produced at one time. In conclusion, these synonyms for "stack" effectively convey the meaning of a collection of objects placed one on top of the other.