horizon
1. [ noun ] the line at which the sky and Earth appear to meet
Synonyms: visible_horizon sensible_horizon skyline apparent_horizon
Related terms: line perspective
2. [ noun ] the range of interest or activity that can be anticipated
Synonyms: purview view
Examples:

"It is beyond the horizon of present knowledge"

Related terms: scope
3. [ noun ] a specific layer or stratum of soil or subsoil in a vertical cross section of land
Related terms: stratum geological_horizon soil_horizon profile
4. [ noun ] (geography) the great circle on the celestial sphere whose plane passes through the sensible horizon and the center of the Earth
Synonyms: celestial_horizon
Related terms: great_circle
Similar spelling:   horizontal
  Hourigan
  Horrigan