noun
marchioness
The wife or widow of a marquess. A noble title.
侯爵夫人は慈善活動に熱心だった。
The marchioness was devoted to charity work.
侯爵 is the title of marquess itself, while 侯爵夫人 specifically refers to the wife of a marquess.
Compound of 侯爵 (marquess) and 夫人 (wife, lady).