1. A Roman officer who controlled or superintended a particular command, charge, department, etc.; as, the prefect of the aqueducts; the prefect of a camp, of a fleet, of the city guard, of provisions; the pretorian prefect, who was commander of the troops guarding the emperor's person.
2. A superintendent of a department who has control of its police establishment, together with extensive powers of municipal regulation. [France]
3. In the Greek and Roman Catholic churches, a title of certain dignitaries below the rank of bishop.
Apostolic prefect R. C. Ch., the head of a mission, not of episcopal rank.
n : a chief officer or chief magistrate; "the prefect of Paris