- A Friday falling on the 13th day of the month (and therefore doubly ill-omened).
- Any Friday actually darkened by catastrophe.
- The anniversary of a number of catastrophic or unfortunate historical events originally occurring on a Friday.
- (possibly obsolete) Good Friday.
(Simply specific case of etymology 1; listed separately because of popular folk etymology.) Written evidence from 1961 of use by police in Philadelphia in reference to the traffic chaos caused by the large number of shoppers on that day. Later, PR efforts invented the incorrect, more positive "etymology" (which was even in Wiktionary from 2008 to 2015) that the name was given because this day is supposedly the first day of the year on which retailers typically post profits ('in the black') rather than losses ('in the red').
- (US, Canada, business, retailing) The day after U.S. Thanksgiving Day, generally regarded as the first day of the Christmas season, and the busiest shopping day of the year. Observed in the U.S. and, more recently, Canada. (This usage may also very possibly originate in Etymology 1)
- by extension, the sales period involving heavy price reductions immediately following U.S. Thanksgiving Day, from Friday (the original Black Friday) through Monday (Cyber Monday).