adj. Relating to an area that has an urban center surrounded by one or more counties or regions, and that has a population between 10,000 and 50,000; relating to a small city.
2001
The federal government is scheduled to unveil a new classification system in 2003 that will increase the attention given to small communities. Non-metropolitan cities with 10,000-50,000 residents will become known as "micropolitan" areas.
1982 (earliest)
The trick will be to keep that panoramic ambition and that huge driving energy and yet not lose the feeling for small perfections that used to characterize the museum. … But if the big museum is to be what we are asking it to be — the ideal metropolis, in which the art of all times and all places is at home — we must not lose the micropolitan touch.
This word is the smaller, possibly cuter, version of metropolitan (from a Greek word meaning, literally, "mother city"). Micropolitan has been in the news of late because, as the first citation says, the U.S. government is adding the term as a new category of community. (It's estimated that the U.S. contains over 500 of these micropolitan areas.) However, the more general sense of the term is much older, as the earliest citation shows.