A dobshite is one who informs on neighbours or others actions which minor infringements of the law. From the expression to 'dob in ' -to tell someone in authority about something bad that another person has done.

Briefly, "the realization that each random passerby is living a life as vivid and complex as your own." Originally from the Dictionary of Obscure Sorrows, which has a lot more beautiful neologism definitions like this you might enjoy.