what is pi

A letter that is found in the Greek alphabet. Also it's a mathematical term that is most commonly referred to as 3.14 or 22/7. Pi is used in equations to find the circumference and area of a circle as well as the volume of a cylinder, sphere, and cone. 

A pastry cup filled with meat and gravy with a pastry lid

An irrational number (it never ends.) 3.141529265359 and so on.

It's "3.1415926535897923"