/ Dictionary / Index E eon: Meaning and Definition of Find definitions for: e•on Pronunciation: (ē'un, ē'on), [key] — n. an indefinitely long period of time; age. the largest division of geologic time, comprising two or more eras. one billion years. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: eon (Thesaurus) e.o.m. eonian Related Content Daily Word Quiz: cetacean Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language