What is Purge?

Legal Definition
In history, religion, and political science, a purge is the removal of people who are considered undesirable by those in power from a government, another organization, their team owners, or from society as a whole. A group undertaking such an effort is labeled as purging itself. Purges can be either nonviolent or violent; with former often resolved by simple removal from office, and latter with the imprisonment, exile, or murder of those purged.
-- Wikipedia
Legal Definition
To cleanse; to clear; to clear or exonerate from some charge or imputation of guilt or from a contempt.
See also
-- Black's Law Dictionary