From BiblePortal Wikipedia

Webster's Dictionary [1]

(n.) The Evil Principle or Being of the ancient Persians; the Prince of Darkness as opposer to Ormuzd, the King of Light.

Cyclopedia of Biblical, Theological and Ecclesiastical Literature [2]

in Persian mythology, is the evil spirit according to Zoroaster's system of religion. The eternal god Zeruane Akerene created light and darkness (or Ormuzd) and Ahriman, both of whom are eternal and only limited by one another. Both of these were living lonesome and separate, Ormuzd in light and Ahriman in darkness. Then God created the earth, in order that the good might combat with and overcome the evil. He divided the period of the earth's existence into four great ages of three thousand years each. In the first age, light was to rule; in the second, darkness besieged by the light; in the third, light and darkness alternately; in the fourth, the same, ending in the full sway of the light.. Ormuzd created in the first age all that can. be seen, over against which Ahriman placed a frightful creation of darkness, but did not attempt a combat either in the first nor in the second age, although he was asked to do so by his genii. At the end of the second age, feeling himself strong enough, he began war with Ormuzd; he entered heaven himself, but alone, and, filled with wonder and amazement, was thrown down upon the earth. Here he made fire impure by smoke and steam,. devastated everything, and; enveloped all things in a thick darkness, until he was driven back by Ormuzd and thrown into the eternal abyss. Ahriman, however, again roused himself, reached the earth, and made it his habitation. Now the third age began, in which Ahriman created. an evil' spirit for every good spirit created. In the fourth age he is to obtain the superiority, and will cause a comet to fall upon the earth, which will set it on. fire, and change it into a stream of burning metal that shall flow into the eternal pit. Ahriman's kingdom is thus to be entirely burned up. In this way the kingdom' of darkness becomes the kingdom of light; the evil spirits are purified and become good spirits beside the throne of God. SEE ORMUZD.