The Collaborative International Dictionary of English v.0.48:

Forum \Fo"rum\, n.; pl. E. Forums, L. Fora. [L.; akin to
   foris, foras, out of doors. See Foreign.]
   1. A market place or public place in Rome, where causes were
      judicially tried, and orations delivered to the people.
      [1913 Webster]

   2. A tribunal; a court; an assembly empowered to hear and
      decide causes.
      [1913 Webster]

            He [Lord Camden] was . . . more eminent in the
            senate than in the forum.             --Brougham.
      [1913 Webster]