Horizon

ho-rī′zun, n. the circular line formed by the apparent meeting of the earth and sky—in astronomical phrase, the sensible , apparent , or visible horizon , as opposed to the astronomical , true , or rational horizon, the circle formed by a plane pa ing through the centre of the earth, parallel to the sensible horizon, and produced to meet the heavens: ( geol. ) a stratum marked by the presence of a particular fo il not found in the overlying or underlying beds: any level line or surface: the limit of one's experience or apprehension.— adj. Horizon′tal , pertaining to the horizon: parallel to the horizon: level: near the horizon: measured in a plane of the horizon.— n. Horizontal′ity .— adv. Horizon′tally .— Artificial horizon , a small trough containing quicksilver, the surface of which affords a reflection of the celestial bodies. [Fr.,—L.,—Gr. horizōn ( kyklos ), bounding (circle), horizein , to bound— horos , a limit.]