- (uncountable) The state of being contained.
- (uncountable, countable) The state of containing.
- (uncountable, countable) Something contained.
- (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.
- (countable) a physical system designed to prevent the accidental release of radioactive or other dangerous materials from a nuclear reactor or industrial plant.
- (countable, mathematics) an inclusion