Someone who lives or advocates self-denial for any marital activities; especially, for reasons of religious promises or sacred commitments to live and to act in accordance with the rules of a religious order; or the moral conditions that should exist when one is unmarried: According to Catholic beliefs, priests are celibatarians who are mediators between God and humans and being unmarried facilitates the accomplishments of these functions because unmarried priests can be concerned more about the things of God while married priests would have to be more responsible for their families and to consider the rights of their wives; therefore, much of their time and energy would have to be given to nonreligious preoccupations.