In ancient times widows often called themselves 'wèiwángrén' in letters.
Tips
history
Literally 'a person not yet dead.' First attested in the 《左传》 (Spring and Autumn period): a widow used it to mean 'I should have died with my husband but have not yet.' The Confucian framing is grim, a widow's life was treated as borrowed time.
register
Highly literary and now rare. You will see it in historical drama or formal obituaries, almost never in modern speech. Today's neutral term is 寡妇 or, more politely, 遗孀.