1. (n.) The circle 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.

2. (n.) 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.

3. (n.) A plane parallel to the sensible horizon of a place, and passing through the earth's center; -- called also rational / celestial horizon.

4. (n.) The unbroken line separating sky and water, as seen by an eye at a given elevation, no land being visible.

5. (n.) The epoch or time during which a deposit was made.

6. (n.) 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.

azimuth background clear sight color vision command compass cone vision day vision daylight vision discernment domination eye eye-mindedness eyereach eyeshot eyesight false horizon farsight farsightedness field of view field of vision keen sight ken limit of vision limits line of sight naked eye night vision offing outlook outlook over perception peripheral field peripheral vision perspective perspicacity perspicuity photopia power of sight prospect purview quick sight range reach remote distance rod vision scan scope scope of vision scotopia sea line seeing sense of sight sensible horizon sight sightedness sightliness skyline survey sweep the distance twilight vision unobstructed vision vanishing point view visible horizon vision vista visual acuity visual field visual sense