Secret Intelligence Service

The Secret Intelligence Service (SIS), commonly known as MI6 (Military Intelligence, Section 6). is the United Kingdom's external intelligence agency. Under the direction of the Joint Intelligence Committee (JIC), it works alongside the Security Service (MI5), Government Communications Headquarters (GCHQ) and the Defence Intelligence Staff (DIS). May be referred to as 'Box 850' which comes from its old post office box number.
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Noun
1. the government agency in the United Kingdom that is responsible for internal security and counterintelligence overseas
(synonym) MI, Military Intelligence Section 6
(hypernym) international intelligence agency
(classification) United Kingdom, UK, Great Britain, GB, Britain, United Kingdom of Great Britain and Northern Ireland