horizon
NounWordNet 3.0
Noun (4)
- the line at which the sky and Earth appear to meetSynonyms: apparent horizonvisible horizonsensible horizonskyline
- the range of interest or activity that can be anticipated“It is beyond the horizon of present knowledge”Synonyms: viewpurview
- a specific layer or stratum of soil or subsoil in a vertical cross section of land
- the great circle on the celestial sphere whose plane passes through the sensible horizon and the center of the EarthSynonyms: celestial horizon
Webster's Dictionary (GCIDE)
1.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. [1913 Webster]
And when the morning sun shall raise his car Above the border of this horizon.— Shak.[1913 Webster]
All the horizon round Invested with bright rays.— Milton.[1913 Webster]
2.(Astron.) (a) 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. (b) A plane parallel to the sensible horizon of a place, and passing through the earth's center; -- called also rational horizon or celestial horizon. (c) (Naut.) The unbroken line separating sky and water, as seen by an eye at a given elevation, no land being visible. [1913 Webster]
3.(Geol.) The epoch or time during which a deposit was made. [1913 Webster]
The strata all over the earth, which were formed at the same time, are said to belong to the same geological horizon.— Le Conte.[1913 Webster]
4.(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. [1913 Webster]
5.The limit of a person's range of perception, capabilities, or experience; as, children raised in the inner city have limited horizons. [PJC]
6.[fig.] A boundary point or line, or a time point, beyond which new knowledge or experiences may be found; as, more powerful computers are just over the horizon. [PJC]
Apparent horizon. See under Apparent.
Artificial horizon, 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.
Celestial horizon. (Astron.) See def. 2, above.
Dip of the horizon (Astron.), the vertical angle between the sensible horizon and a line to the visible horizon, the latter always being below the former.
Rational horizon, and Sensible horizon. (Astron.) See def. 2, above.
Visible horizon. See definitions 1 and 2, above. [1913 Webster]