continuous decline; on the wane
Describes a situation or entity that is steadily and seemingly irreversibly declining. Often used in formal or written contexts.
That industry is on a path of continuous decline.
The local economy is in steady decline, and no solution has been found.
衰退 means 'decline' or 'decay' as a general noun or verb. 衰退一途 adds the sense of a relentless, one-way course of decline.
一途 means 'one road' or 'single course,' often used in compounds to indicate a steady, unidirectional trend (e.g., 増加一途 'ever-increasing').
Compound of 衰退 (decline) and 一途 (one road, single course), literally 'the one road of decline.'