Word.ws English Dictionary

MI5

MI5 proper noun: the domestic intelligence and counter-espionage agency of the United Kingdom, which operates in secret and whose primary function is to spy on terrorist organizations and others viewed as a threat to British national security. Formally known as the Security Service.

Proper noun

MI5

  1. The domestic intelligence and counter-espionage agency of the United Kingdom, which operates in secret and whose primary function is to spy on terrorist organizations and others viewed as a threat to British national security. Formally known as the Security Service.
    • The service aggressively maintained its position until I produced evidence proving it was untrue - including a recording of one of the calls with a senior MI5 officer.2025 July 6, Daniel De Simone, “How MI5 piled falsehood on falsehood in court in the case of a spy who abused women”, in BBC News, retrieved 06 Jul 2025
    Synonyms:
    Five, 5, Security Service

Synonyms of MI5

Origin of MI5

Abbreviation of Military Intelligence, Section Five.

Questions about MI5

What does MI5 mean?
MI5 means the domestic intelligence and counter-espionage agency of the United Kingdom, which operates in secret and whose primary function is to spy on terrorist organizations and others viewed as a threat to British national security. Formally known as the Security Service.
What part of speech is MI5?
MI5 is a proper noun.

Words near MI5 in the dictionary

  1. mi.
  2. mi./hr
  3. mi./hr.
  4. mi/h
  5. mi/hr
  6. MI5
  7. MI6
  8. MI9
  9. mia
  10. mia luang
  11. Mia Maid

Source and license

Adapted from Wiktionary: MI5 (page history and authors). Text available under the Creative Commons Attribution-ShareAlike 4.0 license. Word.ws reformatted the entry and added links. Wiktionary data of 2026-09-02.

Last updated:

Cite this entry: “MI5.” Word.ws, https://word.ws/mi5. Based on Wiktionary, CC BY-SA 4.0.