A border or boundary established in opposition to another, or the area along a shared border controlled by opposing forces.
From counter- (opposite) + border (boundary line). A relatively modern term combining political and military vocabulary to describe contested border regions.
During the Cold War, counterborders were established along divided nations like Korea and Germany, where two completely opposite political systems literally faced each other across a single line.
Complete word intelligence in one call. Free tier — 50 lookups/day.