A neighbor or fellow tenant who's constantly doing some behavior that is obnoxious, loud, irritating, or unsafe. They are the "thorn in your side" of the building or block.
Phil went to work early this morning and forgot to turn off his regular alarm again. I lay in bed, listening to it beeping for an hour before I gave up and moved to the couch. I think he stole the title of Neighbur" from Nancy, the lady who was always propping the door open for her booty calls.