Q. 1. What does the "indefetibility" of the Catholic Church mean?

A. 1. By the indefectibility of the Catholic Church is meant that the Church, as Jesus Christ founded it, will last until the end of time. The Archangel Gabriel announced to the Blessed Virgin Mary that Christ “shall be king over the house of Jacob forever; and of His kingdom there shall be no end.” [Luke 1:32-33]

"By this term is signified, not merely that the Church will persist to the end of time, but further, that it will be preserved unimpaired in its essential characteristics. The Church can never undergo any constitutional change, which will make it, as a social organism, something different from what it was originally. It can never become corrupt in faith or in morals; nor can it ever lose the Apostolic hierarchy, or the Sacraments through which Christ communicates grace to men."