/ Dictionary / Index A ad initium: Meaning and Definition of Find definitions for: ad i•ni•ti•um Pronunciation: (ad" i-nish'ē-um), [key] at the beginning. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ad init. ad int. Related Content Daily Word Quiz: loathe Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language