Wiktionary
n. An overthrow of a government that is considered an illegitimate regime by external force (especially military might), and its replacement with a new government according to the concept of political legitimacy promoted by that force.
Wikipedia
Regime change is the replacement of one government regime with another. Use of the term dates to at least 1925. Regime change may replace all or part of the state's most critical leadership system, administrative apparatus, or bureaucracy.
It can be the deliberate product of outside force, as in warfare. Rollback is the military strategy to impose a regime change by defeating an enemy and removing its regime by force. Regime change can occur through inside change caused by revolution, coup d'état or reconstruction following the failure of a state.
Usage examples of "regime change".
Clearly, there will be a strategic implication to a regime change in Iraq, if we go forward.
But if we take territory with heavy forces, we hold it and call for a regime change in Damascus.
He also declared that any Iraqi troops who declared a truce in the face of the advancing Allies would be embraced by the coalition and permitted to fight for regime change in their own nation.