Source : Webster's Revised Unabridged Dictionary (1913)

Tribune \Trib"une\, n. [L. tribunus, properly, the chief of a
   tribe, fr. tribus tribe: cf. F. tribun. See {Tribe}.]
   1. (Rom. Antiq.) An officer or magistrate chosen by the
      people, to protect them from the oppression of the
      patricians, or nobles, and to defend their liberties
      against any attempts that might be made upon them by the
      senate and consuls.

   Note: The tribunes were at first two, but their number was
         increased ultimately to ten. There were also military
         tribunes, officers of the army, of whom there were from
         four to six in each legion. Other officers were also
         called tribunes; as, tribunes of the treasury, etc.

   2. Anciently, a bench or elevated place, from which speeches
      were delivered; in France, a kind of pulpit in the hall of
      the legislative assembly, where a member stands while
      making an address; any place occupied by a public orator.

Source : WordNet®

tribune
     n : the apse of a Christian church that contains the bishop's
         throne