'Secret Service' definitions:

Definition of 'Secret Service'

(from WordNet)
noun
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, Secret Service, SS]

Definition of 'Secret service'

From: GCIDE
  • 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. [Webster 1913 Suppl.]