/ Dictionary / Index M myelencephalon: Meaning and Definition of Find definitions for: my•el•en•ceph•a•lon Pronunciation: (mī"u-len-sef'u-lon"), [key] — pl. -lons, -la the posterior section of the hindbrain comprising the medulla oblongata. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: myelencephalon (Thesaurus) myel- myelin Related Content Daily Word Quiz: immense Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language