Source : Webster's Revised Unabridged Dictionary (1913)

Reveille \Re*veil"le\, n. [F. r['e]veil, fr. r['e]veiller to
   awake; pref. re- re- + pref. es- (L. ex) + veiller to awake,
   watch, L. vigilare to watch. The English form was prob. taken
   by mistake from the French imper. r['e]veillez,2d pers. pl.
   See {Vigil}.] (Mil.)
   The beat of drum, or bugle blast, about break of day, to give
   notice that it is time for the soldiers to rise, and for the
   sentinels to forbear challenging. ``Sound a reveille.''
   --Dryden.

         For at dawning to assail ye Here no bugles sound
         reveille.                                --Sir W.
                                                  Scott.

Source : WordNet®

reveille
     n 1: (military) signal to wake up [syn: {wake-up signal}]
     2: a signal to get up in the morning; in the military it is a
        bugle call at sunrise