When your co-worker(s) mysteriously become sick before a holiday. Usually a lazy worker who doesn't want to work before a holiday because he or she would rather be home. A worker who makes up a sickness of some sort to cover for his or her lazy intentions of really notbeing sick.
when someone stands inside of or walks slowly through a doorway while a large number of people are stuck behind them
Guy: "Can you please hurry up? There are atleast 20 people behind you waiting to get inside."
Girl: "I'm sorry, I have Holadayitis and wasn't aware of the line."
Dude these old people must have Holadayitis 'cause they ain't movin'.