1. The profession or skill of preserving or creating friendly relationships between countries: Diplomacy is important between nations so that the concerns and needs are understood, and the skills that guide participants result in decisions that are agreeable on all sides.
2. The management of communication and relationships between nations by members and employees of each nation's government: Diplomacy involves negotiations of treaties, international agreements, etc.
3. The ability to deal with people in a sensitive way that does not upset or offend them or a skillful handling of a situation and the skill and tact in dealing with other people: Tom, the principal of the school, was liked and respected by all of the teachers in his school for his diplomacy because he listened to their problems, was very tactful in his comments and advice when asked, and avoided offending anyone.

Diplomacy is the art of getting other people to do it your way.