Definition of "containment"

containment

/kənˈteɪnmənt/

noun
countable and uncountable, plural containments
1. (uncountable) The state of being contained.
2. (uncountable, countable) The state of containing.
3. (obsolete, uncountable, countable) Something contained.
  Quotations
  The containment of a rich man's estate.The spelling has been modernized.
  1655, Thomas Fuller, edited by James Nichols, The Church History of Britain, […], new edition, volumes (please specify |volume=I to III), London: […] [James Nichols] for Thomas Tegg and Son, […], published 1837
4. (uncountable, countable) A policy of checking the expansion of a hostile foreign power by creating alliances with other states; especially the foreign policy strategy of the United States in the early years of the Cold War.
  Quotations
  Mr. Putin has reinvigorated an alliance that spent years confused about its purpose once it lost the adversary it was formed to contain, the Soviet Union. Now, containment is back.
  2022 February 18, David E. Sanger, “The United States’ Message to Russia: Prove Us Wrong”, in The New York Times‎
5. (countable) A physical system designed to prevent the accidental release of radioactive or other dangerous materials from a nuclear reactor or industrial plant.
6. (countable, mathematics) An inclusion.