We're big fans of Downton Abbey, which aired for six seasons on Masterpiece on PBS and has recently been continued in a feature film. On the show, Dame Maggie Smith plays Violet, Dowager Countess of Grantham, the widowed matriarch of the Crawley family and a source of cutting wit.
Dowager means "a woman holding property or a title from her deceased husband." It comes through French from the Latin word meaning "to endow" and is related to dowry. Using the title dowager countess also distinguishes Violet as the widow of the previous Earl of Grantham from the current countess, Cora.
Another related word is dower, which refers to the property of a deceased husband that is given by law to his widow during her lifetime. The dowager countess lives in the dower house, a smaller house for the widow’s use that is on the same grounds as the family residence.