noun

Each of the twelve chief disciples of Jesus Christ.Any important early Christian teacher, especially St. Paul.The first successful Christian missionary in a country or to a people.A vigorous and pioneering advocate or supporter of a particular policy, idea, or cause.One of the twelve administrative officers in a Church of the Latter-day Saints (Mormons).

This is evident in the lives of the prophets, John the Baptist, the Apostles and the Lord Jesus Christ himself.