from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The hypothetical surface of the earth that coincides everywhere with mean sea level.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A surface of constant gravitational potential at zero elevation.
from The Century Dictionary and Cyclopedia
- n. An imaginary surface which coincides with the mean sea-level over the ocean, and extends under the continents everywhere at that level at which the mean surface of the sea would stand if it were allowed to flow in through a small subterranean canal.
- n. See geode.
German, from Greek geoeidēs, earthlike : gē, earth + -oeidēs, -oid.(American Heritage® Dictionary of the English Language, Fourth Edition)