A major conurbation.
Generally the term describes any densely populated social and economic entity encompassing two or more cities and the increasingly urbanized space between them. It particularly came to describe the urbanized region of the northeastern U.S. that arose in the second half of the 20th century. Stretching between the metropolitan areas of Boston on the northeast to Washington, D.C. , on the southwest, it included the metropolitan areas of New York City , Philadelphia , and Baltimore , Md. The name, meaning "great city," was coined by French geographer Jean Gottmann.