Learn English – What does “sprawling city” mean

The adjective sprawling is used in the expression "sprawling city" because it conveys the idea of something that moves or grows over a large area in a nonordered way:

• The adjective sprawling is good for describing things that extend across a large area. You could describe your school as sprawling if it consists of many buildings spread over several acres.

• It's pretty common to hear a city or its suburbs described as sprawling, since some cities tend to grow that way, spreading their populations out over a large amount of land. You can also describe your brother as sprawling if he likes to sit stretched out on the couch, taking up more than his share of space.

• The verb sprawl is at the root of sprawling, and it comes from an Old English word, spreawlian, "move convulsively." (Vocabulary.com)

Sprawl (n.):

• meaning "straggling expansion of built-up districts into surrounding countryside" is from 1955. (Etymonline)

Note also the expression urban sprawl:

• Urban sprawl or suburban sprawl describes the expansion of human populations away from central urban areas into low-density, monofunctional and usually car-dependent communities, in a process called suburbanization. In addition to describing a particular form of urbanization, the term also relates to the social and environmental consequences associated with this development. (Wikipedia)