from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Any of the four planets, Mercury, Venus, Earth, and Mars, whose orbits are closest to the sun.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Any planet of the Solar System whose orbit is located between the asteroid belt and the sun, i.e., any of Mercury, Venus, Earth, or Mars.
Sorry, no etymologies found.