Cath·ar (kāth'är) n.
pl.Cath·a·ri (-ə-rī') or Cath·ars A member of a Christian sect flourishing in western Europe in the 12th and 13th centuries that professed a dualistic belief emphasizing ascetic renunciation of the world and 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'ar adj., Cath'a·rism n., Cath'a·rist adj. & n.