| An aggregation or continuous network of urban communities.
-Merriam-Webster dictionary, http://www.m-w.com/
An aggregation of contiguous towns or urban areas forming a single community in some respects.
-The New Shorter Oxford English Dictionary
The term "conurbation" is often used as a synonym of megalopolis, i.e. to refer to a conglomeration of several metropolises. However, this usage is somewhat incorrect: a conurbation is simply a continuous built-up area composed of more than one town, while a megalopolis is usually formed by the coalescence of several conurbations. Sometimes a uninuclear conurbation (e.g. Chicago, London) and a polynuclear conurbation (e.g. the San Fransisco-Oakland-San Jose Bay Area) are distinguished between. The term "metropolitan area" is often used in place of "conurbation". | 
