A large and often apparently random aggregation of orbital, asteroidal, or lagrange habitats, manufacturing plants, aioid structures, etc. Dyson swarms of solar power collectors are often found near stars, sometimes including large numbers of habitats as well.
Informal habitat swarms are common in many of the high population solar systems, and can easily include populations of several billions. Often, but not always, living conditions are substandard. The orbital equivalent of a "Sprawl".
Sextans Swarmers - Text by M. Alan Kazlev Nanecology / nanoswarm detected across much of Sextans A (Irregular galaxy - Local Group). It's origin and toposophic nature is unknown. What seem to be a smaller number of similar nanecologies have been detected in Sextans B, showing they were able to make the journey of some million light years separating the two small galaxies.
Sprawl - Text by M. Alan Kazlev When planetary cities grow in an unsystematic and unplanned manner beyond normal boundaries, due to increases in population and industry, so that their suburbs merge into the suburbs of neighbouring cities, the result is a vast extended metropolis called a Sprawl. Sprawls are common on many of the less regulated high population older terraformed planets, and even on moons and planets without a breathable atmosphere or life-supporting environment, such as Luna and Titan in the Sol System. Often, but not always, living conditions are substandard. The planetside equivalent of a "swarm".