Source : Webster's Revised Unabridged Dictionary (1913)

Secret service \Se"cret serv"ice\
   The detective service of a government. In the United States,
   in time of peace the bureau of secret service is under the
   treasury department, and in time of war it aids the war
   department in securing information concerning the movements
   of the enemy.

Source : WordNet®

Secret Service
     n : the United States intelligence agency that protects current
         and former presidents and vice presidents and their
         immediate families and protects distinguished foreign
         visitors; detects and apprehends counterfeiters;
         suppresses forgery of government securities and documents
         [syn: {United States Secret Service}, {US Secret Service},
          {USSS}, {SS}]