noun

1. HORIZON, the range of interest or activity that can be anticipated
2. HORIZON, the line at which the sky and Earth appear to meet
3. HORIZON, the great circle on the celestial sphere whose plane passes through the sensible horizon and the center of the Earth
4. HORIZON, a specific layer or stratum of soil or subsoil in a vertical cross section of land
5. HORIZON, the line where the earth or sea seems to meet the sky
6. HORIZON, the limit or range of a person's knowledge, understanding, or experience
7. HORIZON, the limit of what is possible in a particular field or activity

1. We sailed toward the horizon.
2. The sun rose slowly over the eastern horizon.
3. These discoveries have opened up new horizons in the field of cancer research.