/ Dictionary / Index E eighteenth: Meaning and Definition of Find definitions for: eight•eenth Pronunciation: (ā'tēnth'), [key] — adj. next after the seventeenth; being the ordinal number for 18. being one of 18 equal parts. —n. an eighteenth part, esp. of one (). the eighteenth member of a series. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: eighteenth (Thesaurus) eighteenmo Eighteenth Amendment Related Content Daily Word Quiz: circumspect Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language