\ˈpī \
plural pis\ˈpīz \

Definition of pi 

(Entry 1 of 5)

1 : the 16th letter of the Greek alphabet — see Alphabet Table

2a : the symbol π denoting the ratio of the circumference of a circle to its diameter

b : the ratio itself : a transcendental number having a value rounded to eight decimal places of 3.14159265

\ˈpī \
variants: or less commonly
plural pies

Definition of pi (Entry 2 of 5)

1 : type that is spilled or mixed

2 : a pi character or matrix


variants: or less commonly pie
pied; piing or pieing

Definition of pi (Entry 3 of 5)

transitive verb

: to spill or throw (type or type matter) into disorder

intransitive verb

: to become pied

variants: or less commonly pie

Definition of pi (Entry 4 of 5)

1 : not intended to appear in final printing pi lines

2 : capable of being inserted only by hand pi characters

Definition of PI (Entry 5 of 5)

1 Philippine Islands

2 private investigator

3 programmed instruction

First Known Use of pi

Noun (1)

15th century, in the meaning defined at sense 1

Noun (2)

circa 1659, in the meaning defined at sense 1


1889, in the meaning defined at transitive sense


circa 1940, in the meaning defined at sense 1

History and Etymology for pi

Noun (1)

Middle Greek, from Greek pei, of Semitic origin; akin to Hebrew pe

Noun (2)

origin unknown

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More Definitions for pi


\ˈpī \
plural pis\ˈpīz \

Kids Definition of pi

1 : the symbol π representing the ratio of the circumference of a circle to its diameter

2 : the ratio itself having a value of about 3.1416

Legal Definition of P&I 

(Entry 1 of 2)

principal and interest

Legal Definition of PI (Entry 2 of 2)

private investigator

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More from Merriam-Webster on pi

Rhyming Dictionary: Words that rhyme with pi

Spanish Central: Translation of pi

Nglish: Translation of pi for Spanish Speakers

Britannica.com: Encyclopedia article about pi

Comments on pi

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