Suburb. A suburb is a residential area or a mixed use area, either existing as part of a city or urban area, or as a separate residential community within commuting distance of a city. Some suburbs have a degree of administrative autonomy, and most have lower population densities than inner city neighborhoods.iktionary (0.00 / 0 votes) Rate this definition: suburb (Noun). the area on the periphery of a city or large town that falls between being truly part of the city, but is not countryside either. suburb (Noun).