/ Dictionary / Index T thereinto: Meaning and Definition of Find definitions for: there•in•to Pronunciation: (âr"in't, âr"in-t'), [key] — adv. into that place or thing. into that matter, circumstance, etc. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. thereinafter theremin Related Content Daily Word Quiz: gregarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language