Horizon - Definition

n 1: the line at which the sky and Earth appear to meet [syn:
horizon, apparent horizon, visible horizon, sensible
horizon, skyline]
2: the range of interest or activity that can be anticipated;
"It is beyond the horizon of present knowledge" [syn:
horizon, view, purview]
3: a specific layer or stratum of soil or subsoil in a vertical
cross section of land
4: the great circle on the celestial sphere whose plane passes
through the sensible horizon and the center of the Earth
[syn: horizon, celestial horizon]