Pi is the 16th letter of the Greek alphabet, or the numerical value of the ratio of the circumference of a circle to its diameter.(noun)
See pi in Webster's New World College Dictionary
Origin: Gr pi, earlier pei < Sem, as in Heb pē
See pi in American Heritage Dictionary 4
Origin: Late Greek pī
Origin: , from Greek pei
Origin: , of Phoenician origin; see p in Semitic roots.
Learn more about pi