level ground; flat land
Refers to a flat, horizontal surface of the earth; often used in geographical or descriptive contexts.
このあたりは地平が続いている。
The level ground stretches on around here.
field of view; visible range
Rare usage referring to the extent of what one can see; more commonly expressed as 視界 or 視野.
地平の彼方に山々が見える。
Mountains are visible in the far distance.
Compound of 地 (earth, ground) and 平 (flat, level). The meaning 'horizon' is an abbreviation of 地平線.