We found 13 dictionaries that define the word light speed:

General (10 matching dictionaries)

1. light speed: Merriam-Webster
2. light speed: Vocabulary.com
3. light-speed: Wordnik
4. light speed: Wiktionary
5. light speed: Dictionary.com
6. Light Speed, Light-speed, Light speed: Wikipedia, the Free Encyclopedia
7. light speed: Rhymezone
8. light speed: FreeDictionary.org
9. light speed: Mnemonic Dictionary
10. light speed: TheFreeDictionary.com

Computing (1 matching dictionary)

11. light speed: Encyclopedia

Slang (1 matching dictionary)

12. Light Speed: Urban Dictionary

Tech (1 matching dictionary)

13. Basics of Space Flight Glossary (No longer online)

(Note: See light_speeds as well.)

Definitions from Wiktionary (Light speed) ▸ noun:  Alternative form of lightspeed [The speed of light (in vacuum unless another medium is specified).] ▸ Words similar to light speed ▸ Usage examples for light speed ▸ Idioms related to light speed ▸ Wikipedia articles (New!) ▸ Words that often appear near light speed ▸ Rhymes of light speed ▸ Invented words related to light speed