1.
If a law or principle is ~, you must not break it. (FORMAL)
The game had a single ~ rule: obstacles were to be overcome, not circumvented.
ADJ
2.
If a country says its borders are ~, it means they must not be changed or crossed without permission. (FORMAL)
Yesterday’s resolution says the present Polish border is ‘~’.
ADJ
inviolability
Parliament has recognised the inviolability of the current border.
N-UNCOUNT