Definition

/paɪ/

noun

The 16th letter of the Classical and Modern Greek alphabets and the seventeenth in Old Greek.
An irrational and transcendental constant representing the ratio of the circumference of a Euclidean circle to its diameter; approximately 3.14159265358979323846264338327950; usually written π.
Metal type that has been spilled, mixed together, or disordered.

verb

adjective

Not part of the usual font character set; especially, non-Roman type or symbols as opposed to standard alphanumeric Roman type.
“In computing, pi characters may be entered with special key combinations.”