Blackout Wednesday (also known as Drinksgiving) refers to binge drinking on the night before the Thanksgiving holiday in the United States.
Very few people work on Thanksgiving, and most college students are home with their families for the Thanksgiving holiday, which means that high school friends have an opportunity to catch up at the local tavern as they converge on their hometown.
"Blacking out" is a slang term for unconsciousness and/or memory loss due to excessive alcohol intoxication. In some suburbs of Chicago, Blackout Wednesday can be a more popular party night than even New Year's Eve or Saint Patrick's Day. In some cities, it is the worst drunk driving night of the year.