What does PI stand for?

What does PI mean?

PI	Pure Imported Governmental » US Government
PI	Pilipino Insurrecto Governmental » Military
PI	Publications Inquiry Community » Media
PI	Problem Investigator Business » Positions
PI	Pool Instructor Business » Positions
PI	Paducah and Illinois Railroad Regional » Railroads
PI	Pareto Improved Academic & Science » Mathematics
PI	Phantom Investigator Miscellaneous » Funnies
PI	Participating Informant Community » Law
PI	Post Inaccrochable Community » Media
PI	Patternology International Business » Firms
PI	Pengajian Inggeris Academic & Science » Universities
PI	Perpetual Idiosy Medical » Physiology
PI	Pisa (Provence) International » Italian
PI	Petrol Injection Business » Products
PI	Power Improved Business » Products
PI	Public Inquiry Academic & Science » Libraries
PI	Perlite Institute Business » Professional Organizations
PI	Paramagnetic Insulator Business » Products
PI	Professionalism and Integrity Business » General
PI	Program Introduction Governmental » NASA
PI	Procurement Item Governmental » NASA
PI	Preliminary Investigation Governmental » NASA
PI	Pen and Ink (Document Update) Governmental » NASA
PI	Payload Interrogator Governmental » NASA