✨📕 The NEWThe NEW Collegiate Dictionary, 12th Edition Over 5,000 words added — Buy Now! Collegiate Dictionary — Buy Now!

medullary sheath

noun

: myelin sheath

Word History

First Known Use

circa 1846, in the meaning defined above

Time Traveler
The first known use of medullary sheath was circa 1846

Rhymes for medullary sheath

See All Rhymes for medullary sheath

Browse Nearby Words

medullary ray
medullary sheath
medullary spot
See all Nearby Words

Cite this Entry

“Medullary sheath.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/medullary%20sheath. Accessed 30 Nov. 2025.

Copy Citation

Share

Medical Definition

medullary sheath

noun
: myelin sheath
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 More

31 Useful Rhetorical Devices

'Affect' vs. 'Effect'

The Difference Between 'i.e.' and 'e.g.'

Why is '-ed' sometimes pronounced at the end of a word?

What’s the difference between ‘cemetery’ and ‘graveyard’?
See More

Popular in Wordplay

See More

Are you in a 'food coma'?

The Words of the Week - Nov. 28

17 Words for Dog Breeds

Words That Turned 100 in 2025

How 'Namaste' Entered The English Language
See More

Popular

See More

31 Useful Rhetorical Devices

Are you in a 'food coma'?

The Words of the Week - Nov. 28
See More

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 Pick the best words!
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?
The Missing Letter A daily crossword with a twist
petit-fours
Name That Dessert! Hope you’ve saved room for some sweet vocabulary.
See All