/ Dictionary / Index A archencephalon: Meaning and Definition of Find definitions for: arch•en•ceph•a•lon Pronunciation: (är"ken-sef'u-lon"), [key] — n. Embryol. the primitive forebrain region of the embryo, anterior to the notochord, that gives rise to the midbrain and forebrain. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Archemorus archenemy Related Content Daily Word Quiz: careening Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language