Containment

1. That which is contained; the extent; the substance.
2. the act of containing.
3. (Diplomacy) the act or policy of restricting the influence or territorial growth of a hostile nation.
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.
5. a structure surrounding a nuclear power plant designed to prevent release of radioactive materials into the environment in the event of an accident.

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