nounThe American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Either of two ecumenical councils of the Roman Catholic Church, the First Vatican Council (1869-1870) and the Second Vatican Council (1962-1965), convoked by Pius IX and John XXIII, respectively. The First is noted for its affirmation of papal infallibility, and the Second resulted in the revision of most of the liturgy, the replacement of Latin with vernacular languages in rites, and more open relationships with non-Catholic denominations.