/ Dictionary / Index T thereunder: Meaning and Definition of Find definitions for: there•un•der Pronunciation: (âr"un'dur), [key] — adv. under or beneath that. under the authority of or in accordance with that. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: thereunder (Thesaurus) theretofore thereupon Related Content Daily Word Quiz: perspicacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language