We found 20 dictionaries that define the word leap second:

General (13 matching dictionaries)

1. leap second: Merriam-Webster
2. leap second: Oxford Learner's Dictionaries
3. leap second: American Heritage Dictionary of the English Language
4. leap second: Collins English Dictionary
5. leap second: Vocabulary.com
6. leap second: Wiktionary
7. leap second: Infoplease Dictionary
8. leap second: Dictionary.com
9. Leap Second, Leap second: Wikipedia, the Free Encyclopedia
10. leap second: Rhymezone
11. leap second: FreeDictionary.org
12. leap second: Mnemonic Dictionary
13. leap second: TheFreeDictionary.com

Computing (2 matching dictionaries)

14. leap second: Free On-line Dictionary of Computing
15. Leap-second, leap second: Encyclopedia

Medicine (1 matching dictionary)

16. online medical dictionary (No longer online)

Science (3 matching dictionaries)

17. Leap Second: Eric Weisstein's World of Astronomy
18. Leap Second: Extragalactic Astronomy
19. How Many? A Dictionary of Units of Measurement (No longer online)

Tech (1 matching dictionary)

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

(Note: See leap_seconds as well.)

Definitions from Wiktionary (leap second) ▸ noun:  A second of time added to the year occasionally to compensate for variation in the rate of Earth's rotation relative to the absolute standards of time. Similar: leap day, leap year, bissextile year, leap week, terasecond, split second, just a second, Sec., bissextile month, year, more... Opposite: subtractive second, deletion second Types: positive, negative, more... ▸ Words similar to leap second ▸ Usage examples for leap second ▸ Idioms related to leap second ▸ Wikipedia articles (New!) ▸ Words that often appear near leap second ▸ Rhymes of leap second ▸ Invented words related to leap second