pi /paɪ/ noun [uncountable]
[Date: 1800-1900; Origin: From the name of the first letter of Greek periphereia 'distance around a circle']
technical a number that is represented by the Greek letter (π) and is equal to the distance around a circle, divided by its width

[TahlilGaran] Dictionary of Contemporary English ▲

PI
[not an acronym] name for Greek symbol representing the ratio of an area of a circle to its radius; approximately 3.1416 
Per Inquiry 
Philippine Islands (slang) 
Politically Incorrect 
Polyisocyanurate (rigid foam contruction material) 
Private Investigator

[TahlilGaran] Acronyms and Abbreviations Dictionary ▲

P.I.
Personal injury

[TahlilGaran] Acronyms and Abbreviations Dictionary ▲