Opus Dei

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A Roman Catholic organization composed of both clergy and lay members and dedicated to fostering Christian principles at all levels of society.

Wiktionary

1. n. short for The Prelature of the Holy Cross and Opus Dei, a Roman Catholic organization composed of a prelate, secular clergy and lay people whose mission is to spread the Catholic teaching that everyone is called to become a saint; its lay members, men and women, engage in the affairs of the world and seek to direct them "according to God's will".