Definition of MI6 in English:

MI6

proper noun

  • (in the UK) the governmental agency responsible for dealing with matters of internal security and counter-intelligence overseas. Formed in 1912, the agency was officially named the Secret Intelligence Service in 1964, but the name MI6 remains in popular use.

Origin

From Military Intelligence section 5.

Pronunciation:

MI6

/ɛmʌɪˈsɪks/