Noun
Pronunciation: /ˈmeɡəsɪti/ (plural: megacities)
A megacity is a very large city, usually defined as one with a population exceeding 10 million people.
Megacities represent some of the most densely populated urban areas in the world, often characterized by significant economic, cultural, and social influence.
Author's summary:
A megacity is typically a metropolitan area with more than 10 million residents, marking it as a major hub of population and activity.