The Soka Gakkai Dictionary of Buddhism
wheel-turning king[転輪聖王・転輪王・輪王] (Skt chakravarti-raja, chakravarti-rajan, or chakravartin; Jpn tenrin-jo’o, tenrin-o, or rin-o )
Also, wheel-turning sage king, or wheel-king. An ideal ruler in ancient Indian mythology who governs with justice rather than force and brings tranquillity and comfort to the people. He possesses seven treasures: a wheel, elephants, horses, jewels, jewel-like women, excellent ministers of financial affairs, and generals. He also possesses the thirty-two features as a Buddha does, as well as the four virtues of great wealth, admirable features and form, freedom from worries, and long life. According to some scriptures, when Shakyamuni was born, a hermit-sage named Asita foretold that, if the boy remained in the secular world, he would become a wheel-turning king, but if he renounced secular life, he would become a Buddha.
While turning the wheel he was given by heaven, a wheel-turning king advances everywhere at will and establishes peace. These wheels are of four kinds: gold, silver, copper, and iron, the type of wheel indicating a wheel-turning king's rank, or the extent of his realm and power. A gold-wheel-turning king rules all the four continents surrounding Mount Sumeru; a silver-wheel-turning king, the eastern, western, and southern continents; a copper-wheel-turning king, the eastern and southern continents; and an iron-wheel-turning king, the southern continent, or Jambudvipa. Buddhist scriptures contain stories of Shakyamuni Buddha's previous incarnations as a wheel-turning king.