pi

1
[ pahy ]
/ paɪ /

noun, plural pis.

the 16th letter of the Greek alphabet (II, π).
the consonant sound represented by this letter.
Mathematics.
  1. the letter π, used as the symbol for the ratio of the circumference of a circle to its diameter.
  2. the ratio itself: 3.141592+.

Origin of pi

1
1835–45; < Greek pî, peî; used in mathematics to represent Greek periphérion periphery

Definition for pi (2 of 5)

pi2

or pie

[ pahy ]
/ paɪ /

noun, plural pies.

printing types mixed together indiscriminately.
any confused mixture; jumble.

verb (used with object), pied, pi·ing.

to reduce (printing types) to a state of confusion.
to jumble.

Origin of pi

2
First recorded in 1650–60; origin uncertain

Definition for pi (3 of 5)

PI

Law. personal injury.
principal investigator.
Also P.I., p.i. private investigator.

Definition for pi (4 of 5)

Pi.

or pi.


Definition for pi (5 of 5)

P.I.

Philippine Islands.
Also PI, p.i. private investigator.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

Examples from the Web for pi

British Dictionary definitions for pi (1 of 4)

pi1
/ (paɪ) /

noun plural pis

the 16th letter in the Greek alphabet (Π, π), a consonant, transliterated as p
maths a transcendental number, fundamental to mathematics, that is the ratio of the circumference of a circle to its diameter. Approximate value: 3.141 592…; symbol: π

Word Origin for pi

C18 (mathematical use): representing the first letter of Greek periphereia periphery

British Dictionary definitions for pi (2 of 4)

pi2

pie

/ (paɪ) /

noun plural pies

a jumbled pile of printer's type
a jumbled mixture

verb pies, piing, pied, pies, pieing or pied (tr)

to spill and mix (set type) indiscriminately
to mix up

Word Origin for pi

C17: of uncertain origin

British Dictionary definitions for pi (3 of 4)

pi3
/ (paɪ) /

adjective

British slang short for pious (def. 2), pious (def. 3)

British Dictionary definitions for pi (4 of 4)

PI

abbreviation for

Philippine Islands
private investigator
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for pi (1 of 2)

pi
[ pī ]

n. pl. pis

The 16th letter of the Greek alphabet.

Medical definitions for pi (2 of 2)

pI
[ pēī ]

n.

The pH value for the isoelectric point of a given substance in solution.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Scientific definitions for pi

pi
[ pī ]

An irrational number that has a numerical value of 3.14159265358979… and is represented by the symbol π. It expresses the ratio of the circumference to the diameter of a circle and appears in many mathematical expressions.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

Cultural definitions for pi

pi
[ (peye) ]

The irrational number obtained by dividing the length of the diameter of a circle into its circumference. Pi is approximately 3.1416. The sign for pi is π.

The New Dictionary of Cultural Literacy, Third Edition Copyright © 2005 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.