from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun The apparent intersection of the earth and sky as seen by an observer.
  • noun The limit or edge of the observable universe.
  • noun The range of one's knowledge, experience, or interest.
  • noun A specific position in a column of rock layers, usually designated by the occurrence of one or more distinctive fossils or by a distinctive sediment bed, that is used in stratigraphy.
  • noun A layer of soil that can be distinguished from adjacent layers of soil and that is characterized by a certain color, texture, structure or chemical composition.
  • noun Archaeology A period during which the influence of a specified culture spread rapidly over a defined area.

from The Century Dictionary.

  • To limit or bound by a horizon.
  • noun The circle which at sea forms the apparent boundary between sea and sky, and on land would bound the sky were all terrestrial obstructions down to the sea-level removed. Called the apparent, sensible, or visible horizon, in distinction from the astronomical horizon (which see, below).
  • noun Hence The line that bounds the view; the limit of vision.
  • noun Figuratively, the limit of intellectual perception, of experience, or of knowledge.
  • noun In geology, a stratum or group of strata characterized by the presence of a particular fossil not found in the underlying or overlying beds, or of a peculiar assemblage of fossils.
  • noun In zoology and anatomy, a level or horizontal line or surface: as, the horizon of the teeth; the horizon of the diaphragm

from the GNU version of the Collaborative International Dictionary of English.

  • noun The line which bounds that part of the earth's surface visible to a spectator from a given point; the apparent junction of the earth and sky.
  • noun A plane passing through the eye of the spectator and at right angles to the vertical at a given place; a plane tangent to the earth's surface at that place; called distinctively the sensible horizon.
  • noun A plane parallel to the sensible horizon of a place, and passing through the earth's center; -- called also rational horizon or celestial horizon.
  • noun (Naut.) The unbroken line separating sky and water, as seen by an eye at a given elevation, no land being visible.
  • noun (Geol.) The epoch or time during which a deposit was made.
  • noun (Painting) The chief horizontal line in a picture of any sort, which determines in the picture the height of the eye of the spectator; in an extended landscape, the representation of the natural horizon corresponds with this line.
  • noun The limit of a person's range of perception, capabilities, or experience.
  • noun A boundary point or line, or a time point, beyond which new knowledge or experiences may be found.
  • noun See under Apparent.
  • noun a level mirror, as the surface of mercury in a shallow vessel, or a plane reflector adjusted to the true level artificially; -- used chiefly with the sextant for observing the double altitude of a celestial body.
  • noun (Astron.) See def. 2, above.
  • noun (Astron.) the vertical angle between the sensible horizon and a line to the visible horizon, the latter always being below the former.
  • noun (Astron.) See def. 2, above.
  • noun See definitions 1 and 2, above.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun The horizontal line that appears to separate the Earth from the sky.
  • noun The range or limit of one's knowledge, experience or interest.
  • noun geology A specific layer of soil or strata
  • noun archaeology, US A cultural sub-period or level within a more encompassing time period.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun a specific layer or stratum of soil or subsoil in a vertical cross section of land
  • noun the great circle on the celestial sphere whose plane passes through the sensible horizon and the center of the Earth
  • noun the line at which the sky and Earth appear to meet
  • noun the range of interest or activity that can be anticipated


from The American Heritage® Dictionary of the English Language, 4th Edition

[Middle English orizon, from Old French, from Latin horizōn, from Greek horizōn (kuklos), limiting (circle), horizon, present participle of horizein, to limit, from horos, boundary.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From Ancient Greek ὁρίζων (horizōn), from ὅρος (horos, "boundary")


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  • January 17, 2007