A fork of Rural Dictionary
What one who works a full-time job will catch at a certain point in the week where they are no longer willing to do work in anticipation to the upcoming weekend; similar to the more popular 'senioritis' often found in high schools.
On Thursday afternoon Stacy threw down her work and said "I'm done, I'm not doing anymore, I've got a severe case of weekenditis," as she strolled off to the break room for an undetermined amount of time.