Mis·tress n.
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.
The late queen's gentlewoman! a knight's daughter!
To be her mistress' mistress! --Shak.
2. A woman well skilled in anything, or having the mastery over it.
A letter desires all young wives to make themselves mistresses of Wingate's Arithmetic. --Addison.
3. A woman regarded with love and devotion; she who has command over one's heart; a beloved object; a sweetheart. [Poetic]
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.
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 A title of courtesy formerly prefixed to the name of a woman, married or unmarried, but now superseded by the contracted forms, Mrs., for a married, and Miss, for an unmarried, woman.
Now Mistress Gilpin (careful soul). --Cowper.
6. A married woman; a wife. [Scot.]
Several of the neighboring mistresses had assembled to witness the event of this memorable evening. --Sir W. Scott.
7. The old name of the jack at bowls.
To be one's own mistress, to be exempt from control by another person.