Source : Webster's Revised Unabridged Dictionary (1913)

Militia \Mi*li"tia\, n. [L., military service, soldiery, fr.
   miles, militis, soldier: cf. F. milice.]
   1. In the widest sense, the whole military force of a nation,
      including both those engaged in military service as a
      business, and those competent and available for such
      service; specifically, the body of citizens enrolled for
      military instruction and discipline, but not subject to be
      called into actual service except in emergencies.

            The king's captains and soldiers fight his battles,
            and yet . . . the power of the militia is he. --Jer.
                                                  Taylor.

   2. Military service; warfare. [Obs.] --Baxter.

Source : WordNet®

militia
     n 1: civilians trained as soldiers but not part of the regular
          army [syn: {reserves}]
     2: the entire body of physically fit civilians eligible by law
        for military service; "their troops were untrained
        militia"; "Congress shall have power to provide for
        calling forth the militia"--United States Constitution