Interagency means two or more organisations — often different parts of a government — working on the same problem together. An interagency meeting is not inside one office. Police, health, and education might sit at one table. News and official papers love this word. In daily talk, people just say “different departments working together.” The inter- here really does mean “between.” Though actually, it is not only national government: a city and a charity can have an interagency plan too. It just sounds most at home in reports and meetings.

跨部會的、機構間的。台灣公文常用「跨部會」；中國大陸較常說「跨部門」。