Question

define pie in short word

Answer 1

Pie refers to a specific number that is 22/7 or 3.14 that is used in area of circle ,cylinders and perimeter.
I have edited the answer because I thought that you want to know pie chart.

Answer 2

The number π is a mathematical constant. Originally defined as the ratio of a circle's circumference to its diameter, it now has various equivalent definitions and appears in many formulas in all areas of mathematics and physics.