Of broad or liberal scope; comprehensive: "The 100-odd pages of formulas and constants are surely the most catholic to be found\u201d ( Scientific American). Including or concerning all humankind; universal: "what was of catholic rather than national interest\u201d ( J.A. Froude). Of or involving the Roman Catholic Church. Of or relating to the universal Christian church. Of or relating to the ancient undivided Christian church. Of or relating to those churches that have claimed to be representatives of the ancient undivided church. A member of a Catholic church, especially a Roman Catholic.