Pronunciation: (yoor'u-nus, yoo-rā'-),[key] —n. 1. Astron.the planet seventh in order from the sun, having an equatorial diameter of 32,600 miles (56,460 km), a mean distance from the sun of 1,784 million miles (2,871 million km), a period of revolution of 84.07 years, and 15 moons. See table under planet. 2. Also,Ouranos.Class. Myth.the personification of Heaven and ruler of the world, son and husband of Gaea (Earth) and father of the Titans, who was castrated and dethroned by his youngest son, Cronus, at the instigation of Gaea.