- a city with over 10 million inhabitants
WordReference Random House Unabridged Dictionary of American English © 2026
meg•a•cit•y
(meg′ə sit′ē),USA pronunciation n., pl. -cit•ies.
- a city having a population of one million or more.
- mega- + city 1965–70
Collins Concise English Dictionary © HarperCollins Publishers::
megacity /ˈmɛɡəˌsɪtɪ/ n ( pl -cities)