Be sure to ask in your PIR group as well.
It stands for Pass-in-Review and is another way to say graduation form Boot Camp. Your PIR group is PIR 12/13/2013 TG 05- 8 Divisions (037-042, 905 and 906).
The Page, What does ??? mean? (A Guide to Navy Abbreviations and Terminology), will help you with many of the new terms you will come across. That Page is within Boot Camp Moms (and loved ones) and I invite you to join while you are there. There is lots of info for you in the Pages there and in your PIR group.