Wiktionary
megacities
n. (plural of megacity English)
Usage examples of "megacities".
After it escaped from the processing plants, it spread through all the megacities and we've had to abandon huge areas to it.
To the scouting party it was only minutes since they'd entered the wormhole, but as soon as they came out they found a sterile planet, with the ruins of the megacities crumbling into dust.
We went from small villages where everybody knew each other to megacities in a matter of a few centuries—before we had the ability to evolve emotionally tougher hides.