What is "gigacity"

n. A city even larger in scale than a megacity.

Gigacity is a city with a population of more than 100 millions. No such cities exist today, but announcements by the government of China in 2014 could lead to the worlds' first gigacity. According to the Nanfang Insider, the economic integration of megacity Beijing, megacity Tianjin and eight cities (prefectures) in the province of Hebei would result in a city of 130 million.