When a male student in college, high school, middle school, hell even elementary school is sitting in class and for no apparent reason, they get hard wood.
Often occurs in the most boring class of the day. It also always seems to occur right before the end of class, so you look awkward as fuck with your hands in your pockets if you don't have an object to conceal it.
Guy 1: Hey did you see that bro over there adjusting his pants with his hands in his pockets when class ended?
Guy 2: Yea I slipped him my notebook to cover his RCB