Emily Dickinson Lexicon

MIS'TRESS, n. [Fr. maîtresse; It. maestra, maestressa; Sp. maestra; L. magistra; Ir. maigh is treas. See Master.]

1. A woman who governs; correlative to servant, slave, or subject. My mistress here lies murdered in her bed. Shak.
2. The female head of a family.
3. That which governs; a sovereign. Rome was mistress of the world.
4. One that commands, or has possession and sovereignty. The queen is mistress of the Indies.
5. A female who is well skilled in any thing; as, she is mistress of arithmetic.
6. A woman teacher; an instructress of a school. Swift.
7. A woman beloved and courted. Clarendon.
8. A woman in keeping for lewd purposes.
9. A term of contemptuous address. Shak.