A woman having power, authority, or ownership; a woman who exercises authority, is chief, etc.; the female head of a family, a school, etc.
- A woman who has a continuing sexual relationship with a usually married man who is not her husband and from whom she generally receives material support.
- A woman in a position of authority, control, or ownership, as the head of a household: "Thirteen years had seen her mistress of Kellynch Hall” ( Jane Austen).
- A woman who owns or keeps an animal: a cat sitting in its mistress's lap.
- A woman who owns a slave.
- A woman with ultimate control over something: the mistress of her own mind.
- A nation or country that has supremacy over others: Great Britain, once the mistress of the seas.
- Something personified as female that directs or reigns: "my mistress . . . the open road” ( Robert Louis Stevenson).
- A woman who has mastered a skill or branch of learning: a mistress of the culinary art.
- Used formerly as a courtesy title when speaking to or of a woman.
- Chiefly British A woman schoolteacher.