/ Dictionary / Index B black-letter day: Meaning and Definition of Find definitions for: black'-let"ter day' Pronunciation: (blak'let"ur), [key] an unlucky or tragic day. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. black letter black light Related Content Daily Word Quiz: careening Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language