Black-letter :: Black-letter (a.) Written or printed in black letter; as, a black-letter manuscript or book..
Black-letter :: Black-letter (a.) Given to the study of books in black letter; that is, of old books; out of date..
Black-letter :: Black-letter (a.) Of or pertaining to the days in the calendar not marked with red letters as saints' days. Hence: Unlucky; inauspicious.