| Noun | 1. | Great Wall - a fortification 1,500 miles long built across northern China in the 3rd century BC; is 1,500 miles long and averages 6 meters in widthbulwark, rampart, wall - an embankment built around a space for defensive purposes; "they stormed the ramparts of the city"; "they blew the trumpet and the walls came tumbling down" | |