/ Dictionary / Index T Trinity Sunday: Meaning and Definition of Find definitions for: Trin'ity Sun'day Pronunciation: [key] the Sunday after Pentecost, observed as a festival in honor of the Trinity. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Trinity Trinitytide Related Content Daily Word Quiz: acquiesce Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language