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Definition of MI5 noun from the Oxford Advanced Learner's Dictionary

MI5

noun
 
/ˌem aɪ ˈfaɪv/
 
/ˌem aɪ ˈfaɪv/
[uncountable]
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  1. the British government organization that deals with national security within the UK. Its official name is ‘the Security Service’.
    CultureMI5 is an abbreviation of 'Military Intelligence section 5'. MI5's main activities used to involve protecting British military secrets and catching foreign spies. Since the early 1990s, it has been mainly responsible for collecting information about and dealing with terrorism .MI5 was a very secret organization until the early 1990s, when more information about its activities was made known to the public.
pity
noun
 
 
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