Cathari, or Catharists (Cath`ari, or Catharists) , i.e. purists or puritans, a sect of presumably Gnostic derivation, scattered here and there under different names over the S. and W. of Europe during the Middle Ages, who held the Manichæan doctrine of the radically sinful nature of the flesh, and the necessity of mortifying all its desires and affections to attain purity of soul.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Catesby, Robert * Catharine, St., of Alexandria