matron

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A married woman or a widow, especially a mother of dignity, mature age, and established social position.
• noun A woman who acts as a supervisor or monitor in a public institution, such as a school, hospital, or prison.

from The Century Dictionary.

• noun A married woman, especially an elderly married woman, or a woman old enough to be the mother of a family, whether actually so or not; a woman possessing the gravity suitable to a mother.
• noun In a special sense, a head nurse in a hospital; the female head or superintendent of any institution.

from the GNU version of the Collaborative International Dictionary of English.

• noun A wife or a widow, especially, one who has borne children; a woman of staid or motherly manners.
• noun A housekeeper; esp., a woman who manages the domestic economy of a public instution; a head nurse in a hospital.
• noun (Law) a jury of experienced women called to determine the question of pregnancy when set up in bar of execution, and for other cognate purposes.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A mature woman; a wife or a widow, especially, one who has borne children; a woman of staid or motherly manners.
• noun A housekeeper; especially, a woman who manages the domestic economy of a public institution; a head nurse in a hospital; as, the matron of a school or hospital.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a wardress in a prison
• noun a woman in charge of nursing in a medical institution
• noun a married woman (usually middle-aged with children) who is staid and dignified