on the horizon

WordReference Random House Learner's Dictionary of American English © 2025

ho•ri•zon /həˈraɪzən/   n. 

1. Astronomy [countable] the line or circle that forms what seems to be the boundary between earth and sky.
2. on the horizon, at the limit or range of knowledge, progress, or the like:
   A cure for that disease is now on the horizon.
3. Usually, horizons. [plural] the scope or range of a person's interest:
   Her horizons expanded when she lived abroad for a year.

WordReference Random House Unabridged Dictionary of American English © 2025

ho•ri•zon  (hə rī′zən), n. 

1. Astronomy the line or circle that forms the apparent boundary between earth and sky.
2. Astronomy
   • the small circle of the celestial sphere whose plane is tangent to the earth at the position of a given observer, or the plane of such a circle (sensible horizon.)
   • the great circle of the celestial sphere whose plane passes through the center of the earth and is parallel to the sensible horizon of a given position, or the plane of such a circle (celestial horizon.)
3. the limit or range of perception, knowledge, or the like.
4. Usually, horizons. the scope of a person's interest, education, understanding, etc.:
   His horizons were narrow.
5. Geology a thin, distinctive stratum useful for stratigraphic correlation.
6. Geology, Agriculture any of the series of distinctive layers found in a vertical cross section of any well-developed soil.

• Latin horizontem, accusative of horizōn
• Middle French
• Greek horízōn (kýklos) bounding (circle), equivalent. to horíz(ein) to bound, limit + -ōn present participle suffix (nominative singular); replacing Middle English orizonte
• Latin horizōn
• 1540–50

Synonyms

• 4. world, perspective, domain, viewpoint.