the day of every week that you shave you genitals in order to prepare for any hook-ups for the upcoming weekend.
Shave Day is always the day before the last day of the school week, which means it is usually Thursday.
In the event that you would have no school on Friday, Shave Day would then be Wednesday.
Both male and female should participate in this weekly ritual.
"Everyone get excited! It's Shave Day! I gotta be ready for the weekend and potential hook-ups!"