first lady

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

• noun The wife or hostess of the chief executive of a country, state, or city.
• noun The foremost woman of a specified group or profession.

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

• noun The leading woman in a specified field of endeavor.
• noun Alternative spelling of First Lady.

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

• noun the wife of a chief executive
• noun the leading woman in an art or profession