megacity

noun

1. A very large city; a megalopolis.

   “Why, for instance, do water users in a megacity like Lagos not pay an extra charge to get cesspits pumped out?”

   “For the past four decades, the world’s fastest developing delta has been the Pearl River Delta (PRD) in the province of Guangdong in southern China. The delta area in the Pearl River has been transformed from a predominantly agricultural landscape into one of the world’s largest metropolitan areas, encompassing such megacities as Guangzhou, Dongguan, Shenzhen, Zhuhai, and Hong Kong (Fig. 1.4).”