The Collaborative International Dictionary of English v.0.48:

Pretorium \Pre*to"ri*um\, n. [L. praetorium, fr. praetor.]
   1. The general's tent in a Roman camp; hence, a council of
      war, because held in the general's tent.
      [1913 Webster]

   2. The official residence of a governor of a province; hence,
      a place; a splendid country seat.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pretorium
    n 1: the tent of an ancient Roman general [syn: praetorium,
         pretorium]