사양산업이 · 사양산업을
declining industry, sunset industry
Example
한때 잘나가던 필름 산업은 이제 사양산업이 되었어요.
The once-booming film industry has now become a declining industry.
Word parts
사 slanting+양 sun+산 produce+업 business
Literally 'setting-sun industry' — just like English 'sunset industry.'