noun

1. in ancient Rome, any of various high-ranking officials or chief magistrates in charge of governmental or military departments
2. in modern times, any of various administrative officials; specif.,
   1. the head of a department of France
   2. the chief of the Paris police
3. in some private schools, esp. in England, an older student with disciplinary authority

Etymology: ME prefecte < OFr < L praefectus, pp. of praeficere, to set over: see pre- & -fy