noun

1. a woman who rules others or has control, authority, or power over something; specif.,
   1. a woman who is head of a household or institution
   2. Chiefly Brit. a female schoolteacher
2. a woman very skilled and able in some work, profession, science, art, etc.
3. something personified as a woman that has control, power, etc. England was mistress of the seas
4. 1. a woman who is in a sexual relationship with, and typically is financially supported by, a man without being married to him
   2. a woman who is in an adulterous relationship with a man married to another woman
5. Archaic a sweetheart
6. Obsolete a title used in speaking to or of a woman and placed before the name: now replaced by Mrs., Miss, or Ms.

Etymology: ME maistresse < OFr, fem. of maistre, master