/ Dictionary / Index T theine: Meaning and Definition of Find definitions for: the•ine Pronunciation: (thē'ēn, -in), [key] — n. caffeine, esp. in tea. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Theiler their 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