Webster's Revised Unabridged Dictionary · 1913

Monseigneur

Monseigneur , noun

[French, from mon my + seigneur lord, Latin senior older. See Senior, and compare Monsieur.]

My lord; -- a title in France of a person of high birth or rank; as, Monseigneur the Prince, or Monseigneur the Archibishop. It was given, specifically, to the dauphin, before the Revolution of 1789. (Abbrev. Mgr.)