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n. pl. Cath·a·ri (-ə-rī′) or Cath·ars
A member of a Christian sect flourishing in western Europe in the 1100s and 1200s, whose dualistic belief, embracing asceticism and identifying the world as the creation of a satanic Demiurge, was condemned by the Church as heretical.
[French Cathare, from sing. of Medieval Latin Catharī, from Late Greek Katharoi, from pl. of Greek katharos, pure.]
Cath′a·rist adj. & n.