We found 22 dictionaries that define the word horizontally:

General (18 matching dictionaries)

1. horizontally: Merriam-Webster
2. horizontally: Oxford Learner's Dictionaries
3. horizontally: Collins English Dictionary
4. horizontally: Vocabulary.com
5. Horizontally, horizontally: Wordnik
6. horizontally: Wiktionary
7. Horizontally, horizontally: Dictionary.com
8. Horizontally: Wikipedia, the Free Encyclopedia
9. Horizontally: Online Plain Text English Dictionary
10. horizontally: Webster's Revised Unabridged, 1913 Edition
11. horizontally: Rhymezone
12. Horizontally: AllWords.com Multi-Lingual Dictionary
13. horizontally: Webster's 1828 Dictionary
14. horizontally: FreeDictionary.org
15. horizontally: Mnemonic Dictionary
16. horizontally: TheFreeDictionary.com

Business (1 matching dictionary)

17. horizontally: Merriam-Webster Legal Dictionary

Computing (1 matching dictionary)

18. horizontally: Encyclopedia

Medicine (2 matching dictionaries)

19. horizontally: Merriam-Webster Medical Dictionary
20. horizontally: Medical dictionary

(Note: See horizontal as well.)

Definitions from Wiktionary (horizontally) ▸ adverb:  In a horizontal direction or position. ▸ adverb:  In a horizontal manner (any sense). Similar: vertically, nonhorizontally, over, subhorizontally, nonvertically, horizontically, heightwise, positionally, transversally, directionally, more... Opposite: vertically, upright, perpendicular Types: left, right, center, up, down, north, south, east, west, more... Phrases: spreading horizontally, horizontally long, position horizontally, move horizontally, more... Colors:     sky blue,     sunset orange,     horizon gray,     dawn pink,     ocean teal, more... ▸ Words similar to horizontally ▸ Usage examples for horizontally ▸ Idioms related to horizontally ▸ Wikipedia articles (New!) ▸ Words that often appear near horizontally ▸ Rhymes of horizontally ▸ Invented words related to horizontally