A gristmill is a type of business that produces flour from grain. It typically consists of a large stone wheel that grinds the grain into a powdery substance. A MILLER is a person who works in a gristmill, operating the machinery and overseeing the production of flour. A MILL is a building or structure that houses a gristmill and its associated equipment. All three terms are related to the production of flour and can be used to describe a flour producer.