erstwhile
adj. C1 Advanced US //ˈɝstˌwaɪɫ// UK //ˈɜːstwaɪl// erst·while
adj. something that was true or existed in the past but is no longer the case. You use this to describe a person or thing that has changed over time.
adj. former or previous; relating to a past state or condition that has since changed. Often used to describe a person's former status or a place that has undergone significant transformation.
The erstwhile friend is now a stranger.
The erstwhile leader of the party has since retired from public life and lives in a quiet village.
The erstwhile industrial powerhouse, once a symbol of national pride, now stands as a derelict reminder of a bygone era of economic prosperity.
From erst (“first, formerly”) + while.