The wife or widow of a duke; also, a lady who has the sovereignty of a duchy in her own right.

Anne, the heiress of Buccleuch, who had been married to the unhappy Duke of Monmouth, [bastard] son of Charles II. He was beheaded for his rebellion against James II., 1685.

the wife of a duke or a woman holding ducal title in her own right

the wife of a duke. Her full title would be Duchess+of+title, e.g., Duchess of Wellington

The Duchess is a character invented by Lewis Caroll, who appeared for the first time in Alice's Adventures in Wonderland by Lewis Caroll, in 1865. Caroll does not describe her physically in much detail, although her hideous appearance is strongly established in the popular imagination thanks to John Tenniel's illustrations and from context it is clear that Alice finds her quite unattractive. The Duchess (and the characters which accompany her) is a character that was only added successively, in the 1865 version, and not in the earlier ones.

Duchess is a song by the British band Genesis, appearing as the second track on their 1980 album, Duke.