We found 21 dictionaries that define the word apparent horizon:

General (13 matching dictionaries)

1. apparent horizon: Merriam-Webster
2. apparent horizon: American Heritage Dictionary of the English Language
3. apparent horizon: Collins English Dictionary
4. apparent horizon: Vocabulary.com
5. apparent horizon: Wordnik
6. apparent horizon: Dictionary.com
7. Apparent horizon: Wikipedia, the Free Encyclopedia
8. apparent horizon: Rhymezone
9. apparent horizon: FreeDictionary.org
10. apparent horizon: Mnemonic Dictionary
11. apparent horizon: TheFreeDictionary.com
12. apparent horizon, Apparent horizon: Merriam-Webster

Business (2 matching dictionaries)

13. apparent horizon: Legal dictionary
14. apparent horizon: Financial dictionary

Computing (1 matching dictionary)

15. apparent horizon: Encyclopedia

Medicine (1 matching dictionary)

16. apparent horizon: Medical dictionary

Miscellaneous (1 matching dictionary)

17. apparent horizon: Idioms

Science (1 matching dictionary)

18. Apparent Horizon: Eric Weisstein's World of Physics

Tech (2 matching dictionaries)

19. Glossary of Meteorology (No longer online)
20. SeaTalk Dictionary of English Nautical Language (No longer online)

(Note: See apparent_horizons as well.)

Definitions from Wikipedia (Apparent horizon) ▸ noun:  In general relativity, an apparent horizon is a surface that is the boundary between light rays that are directed outwards and moving outwards and those directed outward but moving inward. Opposite: celestial horizon, true horizon, visible horizon ▸ Words similar to apparent horizon ▸ Usage examples for apparent horizon ▸ Idioms related to apparent horizon ▸ Wikipedia articles (New!) ▸ Words that often appear near apparent horizon ▸ Rhymes of apparent horizon ▸ Invented words related to apparent horizon