/ Dictionary / Index M myelination: Meaning and Definition of Find definitions for: my•e•li•na•tion Pronunciation: (mī"u-lu-nā'shun), [key] — n. Anat. the formation of a myelin sheath. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. myelinated myelin sheath Related Content Daily Word Quiz: feline Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language