- a woman who rules others or has control, authority, or power over something; specif.,
- a woman who is head of a household or institution
- Chiefly Brit. a female schoolteacher
- a woman very skilled and able in some work, profession, science, art, etc.
- [sometimesM-] something personified as a woman that has control, power, etc.: England was mistress of the seas
- a woman who is in a sexual relationship with, and typically is financially supported by, a man without being married to him
- a woman who is in an adulterous relationship with a man married to another woman
- Archaic a sweetheart
- [M-]Obs. a title used in speaking to or of a woman and placed before the name: now replaced by Mrs., Miss, or Ms.
Origin of mistressMiddle English maistresse from OFr, feminine of maistre, master