earth |ərTH|noun1 (also Earth )the planet on which we live; the world: the diversity of life on earth .• the surface of the world as distinct from the sky or the sea: it plummeted back to earth at 60 mph.• the present abode of humankind, as distinct from heaven or hell.The earth is the third planet from the sun in the solar system, orbiting between Venusand Mars at an average distance of 90 million miles (149.6 million km) from the sun, and has one natural satellite, the moon. It has an equatorial diameter of 7,654 miles (12,756 km), an average density 5.5 times that of water, and is believed to have formed about 4,600 million years ago. The earth, which is three-quarters covered by oceans and has a dense atmosphere of nitrogen and oxygen, is the only planet known to support life.2 the substance of the land surface; soil: a layer of earth.• one of the four elements in ancient and medieval philosophy and in astrology (considered essential to certain signs of the zodiac).• a stable, dense, nonvolatile inorganic substance found in the ground.• literary the substance of the human body.3 the underground lair or habitation of a badger or fox.4 Electrical British term for ground1 ( sense 7 of the noun).verb [ with obj. ]1 (earth something up) cover the root and lower stem of a plant with heaped-up earth.2 Hunting drive (a fox) to its underground lair.• [ no obj. ] (of a fox) run to its underground lair.3 Electrical British term for ground1 ( sense 5 of the verb).PHRASEScome (or bring ) back ( down ) to earth return or cause to return to reality after a period of daydreaming or excitement.the earth moved (or did the earth move for you? ) humorous one had (or did you have?) an orgasm.go to earth (of a hunted animal) hide in an underground burrow. • go into hiding: he’d gone to earth after that meeting.like nothing on earth informal very strange: they looked like nothing on earth.on earth used for emphasis: who on earth would venture out in weather like this?ORIGIN Old English eorthe, of Germanic origin; related to Dutch aarde and German Erde .