A green border is a weakly protected section of the national border. The term green border comes from the area covered with vegetation: green borders are usually forests, thickets and meadows, often with varied terrain.
The act of (illegal) crossing to the green border is associated with the phenomenon of smuggling goods and persons of a criminal nature, but it has sometimes also been politically motivated. Green borders are and have been crossed by participants of the political activists illegally operating in their countries to contact with foreign collaborators, allies, emigres and the like, or to emigrate and seek refuge.