To be one's own mistress

Mistress Mis"tress, n. [OE. maistress, OF. maistresse, F. ma[^i]tresse, LL. magistrissa, for L. magistra, fem. of magister. See {Master}, {Mister}, and cf. {Miss} a young woman.] 1. A woman having power, authority, or ownership; a woman who exercises authority, is chief, etc.; the female head of a family, a school, etc. [1913 Webster]

The late queen's gentlewoman! a knight's daughter! To be her mistress' mistress! --Shak. [1913 Webster]

2. A woman well skilled in anything, or having the mastery over it. [1913 Webster]

A letter desires all young wives to make themselves mistresses of Wingate's Arithmetic. --Addison. [1913 Webster]

3. A woman regarded with love and devotion; she who has command over one's heart; a beloved object; a sweetheart. [Poetic] --Clarendon. [1913 Webster]

4. A woman filling the place, but without the rights, of a wife; a woman having an ongoing usually exclusive sexual relationship with a man, who may provide her with financial support in return; a concubine; a loose woman with whom one consorts habitually; as, both his wife and his mistress attended his funeral. --Spectator. [1913 Webster +PJC]

5. A title of courtesy formerly prefixed to the name of a woman, married or unmarried, but now superseded by the contracted forms, Mrs., for a married, and Miss, for an unmarried, woman. [1913 Webster]

Now Mistress Gilpin (careful soul). --Cowper. [1913 Webster]

6. A married woman; a wife. [Scot.] [1913 Webster]

Several of the neighboring mistresses had assembled to witness the event of this memorable evening. --Sir W. Scott. [1913 Webster]

7. The old name of the jack at bowls. --Beau. & Fl. [1913 Webster]

{To be one's own mistress}, to be exempt from control by another person. [1913 Webster]