a woman who has authority, control, or power, esp. the female head of a household, institution, or other establishment.

a woman employing, or in authority over, servants or attendants.

a female owner of an animal, or formerly, a slave.

a woman who has the power of controlling or disposing of something at her own pleasure

mistress of a great fortune.

( sometimes initial capital letter ) something regarded as feminine that has control or supremacy

Great Britain, the mistress of the seas.

a women who is skilled in something, as an occupation or art.

a woman who has a continuing, extramarital sexual relationship with one man, esp. a man who, in return for an exclusive and continuing liaison, provides her with financial support.

British . a female schoolteacher; schoolmistress.

( initial capital letter ) a term of address in former use and corresponding to Mrs., Miss, or Ms.

Archaic . sweetheart.

noun

bedmate , best girl , concubine , courtesan , doxy , dream girl , fancy woman , girlfriend , inamorata , kept woman , ladylove , main squeeze , moll , old lady , other woman , paramour , prostitute , roommate , shack , shack job , sugar , sweetheart , sweetie , amaryllis , amour , chatelaine , corotte , delilah , demimondaine , demirep , dozy , dulcinea , flame , hostess , housekeeper , lorette , lover , materfamilias , matriarch , matron , phryne , superior