Another name for a hangover. Works extremely nicely when you've got already been away consuming until 2am but to get in touch with unwell for work 24 hours later. You can simply say you've got "the flu". It is possible to leave out the "bar" part.Example: Warner: "sorry, mike. I cannot arrived at work today"Mike: "ok"Mike: "Josh, Warner labeled as in sick...says she hasthe flu"Josh: "Yeah....BAR flu."