A totally awesome religion in which the practice consists of eating lots and lots of pistachios and having other people mooch pistachios off of you.
The bigger your mound of pistachio shells on your desk, the more impressive and / or hungry you are.
Also commonly done instead of work that we should probably doing, mainly in Science class.
Founders of Pistachioism : Annie & Michele
( because we are that cool )
Instead of doing Physics work in the back row, we all practice a little Pistachioism instead.