1. A boundary between two territories, regions, or countries that remains fixed and does not change over time
The unchanging border between the two countries has been in place for over a century.
A fronteira imutável entre os dois países está em vigor há mais de um século.
2. A demarcation line that is stable and resistant to modification or dispute
The treaty established an unchanging border to prevent future conflicts.
O tratado estabeleceu uma fronteira imutável para prevenir conflitos futuros.