\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

See 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

What made you want to look up pi? Please tell us where you read or heard it (including the quote, if possible).


evasion of direct action or statement

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