'Wài chéng' literally means 'outer city' — composed of 外 (wài), meaning 'outside' or 'external', and 城 (chéng), meaning 'city' or 'walled city'. Historically, many ancient Chinese cities—especially imperial capitals like Beijing—were built with multiple concentric defensive walls. The wài chéng was the outermost walled enclosure, added later to accommodate population growth and commercial expansion beyond the original inner city (内城, nèi chéng) and imperial city (皇城, huáng chéng).

Today, 'wài chéng' is primarily used in historical, geographical, or urban planning contexts—not as a current administrative term. It appears frequently in academic texts, heritage tours, and discussions about traditional Chinese urban design. While modern Beijing no longer functions as a walled city, districts historically within the outer city—such as Fengtai or Chaoyang south of the old walls—are sometimes referenced using this term for cultural or cartographic precision.