[1] : The Collaborative International Dictionary of English v.0.48

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.

[2] : WordNet (r) 2.0

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
see also:
united states secret service us secret service usss ss 

[3] : Moby Thesaurus II by Grady Ward, 1.0

24 moby thesaurus words for "secret service":
   bow street runner, fbi, fbi agent, federal, g-man, sherlock holmes,
   t-man, detective, fed, hotel detective, house detective,
   house dick, inquiry agent, investigator, narc, operative,
   plainclothesman, police detective, private detective,
   private investigator, revenuer, sleuth, store detective,
   treasury agent

[4] : Moby Thesaurus II by Grady Ward, 1.0

24 moby thesaurus words for "secret service":
   bugging, cloak-and-dagger work, counterespionage,
   counterintelligence, electronic surveillance, espial, espionage,
   following, intelligence, intelligence bureau, intelligence service,
   intelligence work, military intelligence, naval intelligence,
   observation, secret police, shadowing, spying, stakeout,
   surveillance, tailing, trailing, wiretap, wiretapping

Secret Service >> S Words
Secret Service, definition of term: Secret Service
secret+service_pag1.html

Service >> S Words
Service, definition of term: Service
service_pag1.html

Secret >> S Words
Secret, definition of term: Secret
secret_pag1.html

Service Berry >> S Words
Service Berry, definition of term: Service Berry
service+berry_pag1.html

Secret Police >> S Words
Secret Police, definition of term: Secret Police
secret+police_pag1.html

Service Bureau >> S Words
Service Bureau, definition of term: Service Bureau
service+bureau_pag1.html

Civil Service >> C Words
Civil Service, definition of term: Civil Service
civil+service_pag1.html

Lip Service >> L Words
Lip Service, definition of term: Lip Service
lip+service_pag1.html

Channel Service >> C Words
Channel Service, definition of term: Channel Service
channel+service_pag1.html

Public Service >> P Words
Public Service, definition of term: Public Service
public+service_pag1.html