Source : Webster's Revised Unabridged Dictionary (1913)

Headquarters \Head"quar`ters\, n. pl. [but sometimes used as a
   n. sing.]
   The quarters or place of residence of any chief officer, as
   the general in command of an army, or the head of a police
   force; the place from which orders or instructions are
   issued; hence, the center of authority or order.

         The brain, which is the headquarters, or office, of
         intelligence.                            --Collier.

Source : WordNet®

headquarters
     n 1: (usually plural) the office that serves as the
          administrative center of an enterprise; "many companies
          have their headquarters in New York" [syn: {central
          office}, {main office}, {home office}, {home base}]
     2: (usually plural) the military installation from which a
        commander performs the functions of command; "the
        general's headquarters were a couple of large tents" [syn:
         {HQ}, {military headquarters}]
     3: (plural) a military unit consisting of a commander and the
        headquarters staff