[mis.tress] n [ME maistresse, fr. MF, fr. OF, fem. of maistre master--more at master] (15c) 1: a woman who has power, authority, or ownership: as a: the female head of a household b: a woman who employs or supervises servants c: a woman who is in charge of a school or other establishment d: a woman of the Scottish nobility having a status comparable to that of a master
2. a chiefly Brit: a female teacher or tutor b: a woman who has achieved mastery in some field
3: something personified as female that rules, directs, or dominates "when Rome was ~ of the world"
4. a: a woman other than his wife with whom a married man has a continuing sexual relationship b archaic: sweetheart
5. a--used archaically as a title prefixed to the name of a married or unmarried woman b chiefly Southern & Midland: mrs. 1a