adj. & n. (also Zarathustrian)
adj. of or relating to Zoroaster (or Zarathustra) or the dualistic religious system taught by him or his followers in the Zend-Avesta, based on the concept of a conflict between a spirit of light and good and a spirit of darkness and evil.
n. a follower of Zoroaster. Zoroastrianism n.
[ L Zoroastres f. Gk Zoroastres f. Avestan Zarathustra, Persian founder of the religion in the 6th c. BC ]