The visible horizontal line (in all directions) where the sky appears to meet the earth in the distance.

(soil science) The topmost layer of the soil horizons; topsoil

(geology, soil science) The formation of soil horizons

plural of horizon

(philosophy) Relating to a horizon.

(figuratively) Imminent.

(physics) A light-like boundary of the domain of validity of a Cauchy problem. One side of the horizon contains closed space-like geodesics and the other side contains closed time-like geodesics.

plural of Cauchy horizon

A deep in Tonga Trench, Pacific Ocean; the second deepest place on Earth, and deepest part of the Tonga Trench.

(aviation) An instrument that displays the pitch and roll of an aircraft in flight by comparing its attitude to a gyroscopically-maintained indication of the flat horizon line.