/ Dictionary / Index A ad infinitum: Meaning and Definition of Find definitions for: ad in•fi•ni•tum Pronunciation: (ad in"fu-nī'tum, ad" in-), [key] to infinity; endlessly; without limit. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. ad inf. ad init. Related Content Daily Word Quiz: pedagogy Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language