A period of time in schools that require a dress code of dress shirts year-round (and sweaters from October to May.) When the sweaters are no longer required and students don't need to have them on for the rest of the year, pockets are newly exposed. It becomes a contest of who can rip off the most shirt pockets, usually from underclassmen, with the goal being to make a shirt out of just the pockets. It lasts anywhere from a week to two weeks.
Dude #1: Hey look over there!
<Rips pocket off of Dude #2>
Dude #2: ...
Dude #1: Its pocket season, bitch!