Monsieur \Mon*sieur"\, n.; pl. {Messieurs}. [F., fr. mon my + Sieur, abbrev. of seigneur lord. See {Monseigneur}.] 1. The common title of civility in France in speaking to, or of, a man; Mr. or Sir. [Represented by the abbreviation M. or Mons. in the singular, and by {MM.} or {Messrs.} in the plural.] 2. The oldest brother of the king of France. 3. A Frenchman. [Contemptuous] --Shak.