Final answer:
A megalopolis refers to a very large urban region formed by the merging of adjoining cities and suburbs, such as the area around New York City in the U.S.
Step-by-step explanation:
The term used to describe a large urban area formed by the merging of several cities or towns is called a megalopolis. This term denotes a very large urban region that includes multiple adjoining cities and their suburbs. A U.S. example of a megalopolis is the urban corridor surrounding New York City, which was the first of its kind in the country. These areas are characterized by extensive use of natural resources and represent a growing aspect of the U.S. landscape. Factors such as agglomeration economies, which initially bring advantages to such urban areas, can eventually lead to diseconomies like traffic congestion and pollution due to high densities of people and activities.