1the line at which the earth’s surface and the sky appear to meet:the sun rose above the horizon
(also apparent horizon) the circular boundary of the part of the earth’s surface visible from a particular point, ignoring irregularities and obstructions.
(also true horizon) Astronomy a great circle of the celestial sphere, the plane of which passes through the centre of the earth and is parallel to that of the apparent horizon of a place.
2 (often horizons) the limit of a person’s knowledge, experience, or interest:she wanted to leave home and broaden her horizons
3 Geology a layer of soil or rock, or a set of strata, with particular characteristics.
Archaeology a level of an excavated site representing a particular period:the upper horizon of the site showed an arrangement of two rows of features
on the horizon
imminent or just becoming apparent:trouble could be on the horizon
