district consisting of the area on either side of a border or boundary of a country or an area; "the Welsh marches between England and Wales
The borderland between two things is an area which contains features from both of these things so that it is not possible to say that it belongs to one or the other. on the borderland between sleep and waking
The area of land close to the border between two countries or major areas can be called the borderlands. Lebanon's southern borderlands