dowager

A widow holding property or title derived from her late husband.

A reclusive dowager owned the pastures across the river, and her farmhands ran beef cattle on them.

“I don't mean all of your friends—only a small proportion—which, however, connects your circle with that deadly, idle, brainless bunch—the insolent chatterers at the opera, the gorged dowagers, the worn-out, passionless men, the enervated matrons of the summer capital, the chlorotic squatters on huge yachts,[…]!”

The widow of the holder of a title (usually a member of the peerage or a baronet); used in combination with the title she held during her husband's lifetime.

the Earl and Countess of Whiteacre, and the Earl's mother, the dowager Countess of Whiteacre

Sir George Sitwell, Bt. and Lady Sitwell, and Sir George's mother, the dowager Lady Sitwell

Any lady of dignified bearing, especially an older one.

A stately dowager entered the ballroom, and all eyes were upon her.