Zo·ro·as·tri·an·ism (zôr??-?s?tr?-?-n?z??m)n. The religious system founded by Zoroaster and set forth in the Avesta, teaching the worship of Ahura Mazda in the context of a universal struggle between the forces of light and of darkness.Zo?ro·as?tri·an adj. & n.American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.Zoroastrianism (?z?r???æstr??n??z?m) or Zoroastrismn (Other Non-Christian Religions) the dualistic religion founded by the Persian prophet Zoroaster in the late 7th or early 6th centuries bc and set forth in the sacred writings of the Zend-Avesta. It is based on the concept of a continuous struggle between Ormazd (or Ahura Mazda), the god of creation, light, and goodness, and his arch enemy, Ahriman, the spirit of evil and darkness, and it includes a highly developed ethical code. Also called: Mazdaism Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014Zo?ro?as?tri?an?ism (?z?r o??æs tri ??n?z ?m, ?zo?r-) also Zo`ro?as?trism, n. an Iranian religion, founded c600 b.c. by Zoroaster, based on beliefs in a supreme deity, Ahura Mazda, and a cosmic struggle between a spirit of good and a spirit of evil. [1850?55] Random House Kernerman Webster’s College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.Zoroastrianismthe doctrines and practices of a dualistic Iranian religion, especially the existence of a supreme deity, Ahura Mazda, and belief in a cosmic struggle between a spirit of good and light and a spirit of evil and darkness. Also called Zoroastrism, Zarathustrism, Mazdaism. ? Zoroastrian, n., adj.See also: Religion-Ologies & -Isms. Copyright 2008 The Gale Group, Inc. All rights reserved.