Source : Webster's Revised Unabridged Dictionary (1913)

Monsignore \Mon`si*gno"re\, n.; pl. {Monsignors}. [It., my lord.
   Cf. {Monseigneur}.]
   My lord; -- an ecclesiastical dignity bestowed by the pope,
   entitling the bearer to social and domestic rank at the papal
   court. (Abbrev. Mgr.)