eg If I devalue my currency by 99%, and then attempt to pay off debts in that currency, that is a default, regardless of if a country were to try to pretend otherwise. The alternative to that context, would be that any nation can just freely debase their currency, pay back debts in worthless paper, and nobody cares because it's not a default - that's false.
Japan has to debase the Yen to pay its bills. Their government is insolvent due to the extreme debt. They have already defaulted.