What does "purgation" mean?

Purgation: (Law) The clearing of one's self from a crime of which one was publicly suspected and accused. It was either canonical, which was prescribed by the canon law, the form whereof used in the spiritual court was, that the person suspected take his oath that he was clear of the matter objected against him, and bring his honest neighbors with him to make oath that they believes he swore truly; or vulgar, which was by fire or water ordeal, or by combat. See Ordeal. Wharton. Let him put me to my purgation. Shak.