micropolitan

Short definition from Wiktionary

Adjective

1. 1
   Of or pertaining to a city or twin cities having at least 10,000 but fewer than 50,000 inhabitants; of a city: less populated than a metropolitan area but more than a rural one.

Noun

1. 1
   A city or twin cities having at least 10,000 but fewer than 50,000 inhabitants; a city which is less populated than a metropolitan area but more than a rural one.