A neighbor or group of neighbors that aren't pleasant to live near. Usually loud obnoxious drug addicts who
don't have any consideration for the
people they live around. They are loud and unruly in the late hours of night and early AM hours. You get a stroke of luck where you suddenly
don't see them for a few months. They might have been sent to
jail or elsewhere, but you'
re just glad they're finally
gone and that you can live in peace. But then they suddenly come back out of nowhere, back to their old antics and habits. You then realize their absence was temporary - thus the term "boomerang neighbor."
A neighbor you wish would move elsewhere, but they always end up coming back somehow.