ephemeris time

noun

: a uniform measure of time defined by the orbital motions of the planets

Word History

First Known Use

1950, in the meaning defined above

Time Traveler
The first known use of ephemeris time was in 1950

Dictionary Entries Near ephemeris time

ephemeris

ephemeris time

ephemeron

See More Nearby Entries 

Cite this Entry

“Ephemeris time.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/ephemeris%20time. Accessed 25 Apr. 2024.

Copy Citation

Share

More from Merriam-Webster on ephemeris time

Britannica.com: Encyclopedia article about ephemeris time

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Popular in Grammar & Usage

See All

More Commonly Misspelled Words

Commonly Misspelled Words

How to Use Em Dashes (—), En Dashes (–) , and Hyphens (-)

Absent Letters That Are Heard Anyway

How to Use Accents and Diacritical Marks
See All

Popular in Wordplay

See All

The Words of the Week - Apr. 19

10 Words from Taylor Swift Songs (Merriam's Version)

9 Superb Owl Words

10 Words for Lesser-Known Games and Sports

Your Favorite Band is in the Dictionary
See All

Games & Quizzes

See All
Play Quordle: Guess all four words in a limited number of tries. Each of your guesses must be a real 5-letter word.
Quordle Can you solve 4 words at once?
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.
Blossom Word Game You can make only 12 words. Pick the best ones!
Play Missing Letter: a crossword with a twist. Each of the 25 puzzle words start with a different letter of the alphabet. Which letter is missing?
Missing Letter A crossword with a twist
winning words from the national spelling bee logo
Spelling Bee Quiz Can you outdo past winners of the National Spelli...