A locale that is not exactly urban, nor it is rural. It's in a limbo of sorts, marked by a fairly dense population, but not quite as dense as, say, New York City. Suburbs tend to be on the outskirts of a major metropolitan area, a sort of buffer between the city and the country. Suburbia tends to be boring, saturated with gas stations and fast food places and, of course, malls.
See also: Hell