(astrophysics) The gravitational sphere of a black hole within which the escape velocity is greater than the speed of light. / (by extension) A point of no return.

(astronomy) The distance from an observer in a universe beyond which it is impossible for the observer to see, as the light (or other luminal particles) cannot have travelled that distance over the current age of that universe.

The angle of the horizon below the level of the eye.

(computing) A method of preventing routing loops in distance-vector routing protocols by prohibiting a router from advertising a route back onto the interface from which it was learned.

(archaeology) A common set of artefacts that identifies a culture and is found disseminated widely (usually over a number of sites, but sometimes widely over one site) but restricted to a single stratum; a layer or stratum.

A cosmological horizon

Alternative form of archaeological horizon

celestial horizon

(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.

(business) A fixed point of time in the future where certain processes will be evaluated or assumed to end.