Black″–let′ter, a. 1. Written or printed in black letter; as, a black-letter manuscript or book.
2. Given to the study of books in black letter; that is, of old books; out of date.
Kemble, a black-letter man!
J. Boaden.
3. Of or pertaining to the days in the calendar not marked with red letters as saints' days. Hence: Unlucky; inauspicious.