The Collaborative International Dictionary of English v.0.48:

Prefect \Pre"fect\, n. [L. praefectus, fr. praefectus, p. p. of
   praeficere to set over; prae before + facere to make: cf. F.
   pr['e]fet.]
   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.
      [1913 Webster]

   2. A superintendent of a department who has control of its
      police establishment, together with extensive powers of
      municipal regulation. [France] --Brande & C.
      [1913 Webster]

   3. In the Greek and Roman Catholic churches, a title of
      certain dignitaries below the rank of bishop.
      [1913 Webster]

   Apostolic prefect (R. C. Ch.), the head of a mission, not
      of episcopal rank. --Shipley.
      [1913 Webster]