p. i

Dictionary.com Unabridged

P.I.

1.
Philippine Islands.
2.
Also, PI, p.i. private investigator.

private investigator

noun
private detective. Abbreviation: PI, p.i., P.I.

Origin:
1935–40

Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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World English Dictionary
pi1 (paɪ)
 
n , pl pis
1.  the 16th letter in the Greek alphabet (Π, π), a consonant, transliterated as p
2.  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
 
[C18 (mathematical use): representing the first letter of Greek periphereiaperiphery]

pi or pie2 (paɪ)
 
n , pl pies
1.  a jumbled pile of printer's type
2.  a jumbled mixture
 
vb , pies, pies, piing, pied, pies, pieing, pied
3.  to spill and mix (set type) indiscriminately
4.  to mix up
 
[C17: of uncertain origin]
 
pie or pie2
 
n
 
vb
 
[C17: of uncertain origin]

pi3 (paɪ)
 
adj
slang (Brit) pious short for pious

PI
 
abbreviation for
1.  Philippine Islands
2.  private investigator

Collins English Dictionary - Complete & Unabridged 10th Edition
2009 © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009
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Etymonline
Word Origin & History

pi
1841, used in L. 1748 by Swiss mathematician Leonhart Euler (1707-83), from Gk. letter pi (from Heb., lit. "little mouth") as an abbreviation of Gk. periphereia "periphery." For the meaning "printer's term for mixed type," see pie (3).
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Medical Dictionary

pi (pī)
n. pl. pis

Symbol π The 16th letter of the greek alphabet.

pI (pē'ī')
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.
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American Heritage
Science Dictionary
pi   (pī)  Pronunciation Key 
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 © 2002. Published by Houghton Mifflin. All rights reserved.
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American Heritage
Cultural Dictionary
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 American Heritage® New Dictionary of Cultural Literacy, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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American Heritage
Abbreviations & Acronyms
pi
Pali
Pi
inorganic phosphate
PI
  1. performance indicator

  2. politically incorrect

  3. present illness

  4. primary infertility

  5. principal investigator

  6. private investigator

The American Heritage® Abbreviations Dictionary, Third Edition
Copyright © 2005 by Houghton Mifflin Company.
Published by Houghton Mifflin Company. All rights reserved.
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