The Collaborative International Dictionary of English v.0.48:

Pretor \Pre"tor\, n. [L. praetor, for praeitor, fr. praeire to
   go before; prae before + ire to go. See Issue.]
   1. (Rom. Antiq.) A civil officer or magistrate among the
      ancient Romans.
      [1913 Webster]

   Note: Originally the pretor was a kind of third consul; but
         at an early period two pretors were appointed, the
         first of whom (praetor urbanus) was a kind of mayor or
         city judge; the other (praetor peregrinus) was a judge
         of cases in which one or both of the parties were
         foreigners. Still later, the number of pretors, or
         judges, was further increased.
         [1913 Webster]

   2. Hence, a mayor or magistrate. [R.] --Dryden.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pretor
    n 1: an annually elected magistrate of the ancient Roman
         Republic [syn: praetor, pretor]