/ Dictionary / Index T thereat: Meaning and Definition of Find definitions for: there•at Pronunciation: (âr"at'), [key] — adv. at that place or time; there: Seeing the gate, they entered thereat. because of that; thereupon. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. thereafter thereby Related Content Daily Word Quiz: lyceum Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language