NOUN (3)

1. a policy of creating strategic alliances in order to check the expansion of a hostile power or ideology or to force it to negotiate peacefully;
- Example: "containment of communist expansion was a central principle of United States' foreign policy from 1947 to the 1975"

2. (physics) a system designed to prevent the accidental release of radioactive material from a reactor;

3. the act of containing; keeping something from spreading;
- Example: "the containment of the AIDS epidemic"
- Example: "the containment of the rebellion"

The Collaborative International Dictionary of English v.0.48:

Containment \Con*tain"ment\, n.
   1. That which is contained; the extent; the substance. [Obs.]
      [1913 Webster]

            The containment of a rich man's estate. --Fuller.
      [1913 Webster]

   2. the act of containing.
      [PJC]

   3. (Diplomacy) the act or policy of restricting the influence
      or territorial growth of a hostile nation.

   Note: The policy of containment is employed when the defeat
         of a hostile nation or overthrow of its government is
         considered impractical or too costly.
         [PJC]

   4. the act of restricting some deleterious substance within a
      confined space, especially when such material is released
      unintentionally or by accident; as, containment of nuclear
      waste; containment of an oil spill. Also used
      attributively, as a containment boom.
      [PJC]

   5. a structure surrounding a nuclear power plant designed to
      prevent release of radioactive materials into the
      environment in the event of an accident.
      [PJC]

WordNet (r) 3.0 (2006):

containment
    n 1: a policy of creating strategic alliances in order to check
         the expansion of a hostile power or ideology or to force it
         to negotiate peacefully; "containment of communist
         expansion was a central principle of United States' foreign
         policy from 1947 to the 1975"
    2: (physics) a system designed to prevent the accidental release
       of radioactive material from a reactor
    3: the act of containing; keeping something from spreading; "the
       containment of the AIDS epidemic"; "the containment of the
       rebellion"

Moby Thesaurus II by Grady Ward, 1.0:

62 Moby Thesaurus words for "containment":
   Eisenhower Doctrine, Monroe Doctrine, Nixon Doctrine,
   Truman Doctrine, appeasement, balance of power, brinkmanship,
   cincture, circling, circumambience, circumambiency, circumcincture,
   circumflexion, circumjacence, circumposition, coexistence,
   colonialism, compromise, detente, deterrence, diplomacy,
   diplomatic, diplomatics, dollar diplomacy, dollar imperialism,
   embracement, encincture, encirclement, enclosure, encompassment,
   enfoldment, envelopment, environment, expansionism,
   foreign affairs, foreign policy, girding, girdling,
   good-neighbor policy, imperialism, inclusion, internationalism,
   involvement, isolationism, manifest destiny, militarism,
   nationalism, neocolonialism, neutralism, nonresistance, open door,
   open-door policy, peace offensive, peaceful coexistence,
   preparedness, shirt-sleeve diplomacy, shuttle diplomacy,
   spheres of influence, surrounding, the big stick, tough policy,
   world politics