1. Secret Intelligence Service - Noun
2. Secret Intelligence Service - Proper noun
the government agency in the United Kingdom that is responsible for internal security and counterintelligence overseas
Source: WordNetThe Secret Intelligence Service I knew occupied dusky suites of little rooms opposite St James's Park Tube station in London. John le Carré
In early 1971 Heath sent in a Secret Intelligence Service officer, Frank Steele, to talk to the IRA and find out what common ground there was for negotiations. Source: Internet
Bennett had free and unfettered access to the archives of the Foreign Office, as well as those of the Secret Intelligence Service (SIS) and MI5. Source: Internet
Nelipa, p. 306. British Secret Intelligence Service There were two officers of the British Secret Intelligence Service (SIS) in Petrograd at the time. Source: Internet
;Foreign intelligence * Secret Intelligence Service (SIS)/MI6 citation – Foreign intelligence gathering and analysis. Source: Internet
Known as Joint Intelligence Operations, and usually conducted in concert with the Australian Secret Intelligence Service the purpose of these operations is the gathering of security intelligence on and from foreign officials, organisations or companies. Source: Internet