pes'-mak-er: Occurs only in the plural (Mt 5:9, "Blessed are the peacemakers (eirenopoioi): for they shall be called sons of God" (who is "the God of peace")). We have also what seems to be a reflection of this saying in Jas 3:18, "The fruit of righteousness is sown in peace for (the Revised Version margin "by") them that make peace" (tois poiousin eirenen). In classical Greek a "peacemaker" was an ambassador sent to treat of peace. The word in Mt 5:9 would, perhaps, be better rendered "peace-workers," implying not merely making peace between those who are at variance, but working peace as that which is the will of the God of peace for men.
⇒See the definition of peacemaker in the KJV Dictionary
W. L. Walker