The act or operation of cleansing or purifying by separating and carrying off impurities or whatever is superfluous; applied to the body; as, the bowels are cleansed by purgation. So also in pharmacy and in chimistry, medicines, metals and minerals are purified by purgation.

In law, the act of cleansing from a crime, accusation or suspicion of guilt. This was canonical or vulgar. Canonical purgation, prescribed by the canon law, was performed before the bishop or his deputy, and by a jury of twelve clerks. The party accused first made oath to his own innocence, and then the twelve clerks or compurgators swore that they believed he spoke the truth; after which, other witnesses were examined upon oath, on behalf of the prisoner only. Vulgar purgation was performed by the ordeal of fire or water, or by combat.