Definitions
from The American Heritage® Dictionary of the English Language, 4th Edition
 n. The 16th letter of the Greek alphabet. See Table at alphabet.
 n. Mathematics A transcendental number, approximately 3.14159, represented by the symbol π, that expresses the ratio of the circumference to the diameter of a circle and appears as a constant in many mathematical expressions.
 n. An amount of type that has been jumbled or thrown together at random.
 transitive v. To jumble or mix up (type).
 intransitive v. To become jumbled.
from Wiktionary, Creative Commons Attribution/ShareAlike License
 n. The name of the sixteenth letter of the Classical and Modern Greek alphabets and the seventeenth in Old Greek.
 n. An irrational and transcendental constant representing the ratio of the circumference of a Euclidean circle to its diameter; approximately 3.1415926535897932384626433832795; usually written π.
 n. Metal type that has been spilled, mixed together, or disordered. Also called pie.
 v. To spill or mix printing type. Also, "to pie".
 adj. Not part of the usual font character set; especially, nonRoman type or symbols as opposed to standard alphanumeric Roman type.
 abbr. pica (conventionally, 12 points = 1 pica, 6 picas = 1 inch)
 abbr. piaster
from the GNU version of the Collaborative International Dictionary of English
 n. The inorganic orthophoshate ion;  a symbol used in biochemistry.
 n. A mass of type confusedly mixed or unsorted.
 n. A Greek letter (Π, π) corresponding to the Roman letter p.
 n. The letter π, Π, as used to denote the number or quotient approximately expressing the ratio of the circumference of a circle to its diameter; also, the quotient or the ratio itself. The value of the quotient pi, to twenty decimal places, is 3.14159265358979323846 (see note). The number pi is an irrational number, i.e. it cannot be expressed as the quotient of two integers. It is also a transcendental number, i.e. it cannot be expressed as a root of an algebraic equation with a finite number of terms; and from this fact follows the impossibility of the quadrature of the circle by purely algebraic processes, or by the aid of a ruler and compass.
 transitive v. To put into a mixed and disordered condition, as type; to mix and disarrange the type of.
from The Century Dictionary and Cyclopedia
 To reduce (printingtypes) to a state of pi.
 n. Printingtypes mixed together indiscriminately; type in a confused or jumbled condition or mass.
 n. The name of the Greek letter
Π ,π , corresponding to the Roman P, p.  n. The name of a symbol (
π ) used in geometry for the ratio of the circumference of a circle to its diameter. or 3.1415927: first so used by Euler.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
 n. the ratio of the circumference to the diameter of a circle; approximately equal to 3.14159265358979323846...
 n. the 16th letter of the Greek alphabet
 n. someone who can be employed as a detective to collect information
 n. an antiviral drug used against HIV; interrupts HIV replication by binding and blocking HIV protease; often used in combination with other drugs
 n. the scientist in charge of an experiment or research project
Etymologies
from The American Heritage® Dictionary of the English Language, 4th Edition
Examples

PiBook: NoXIB pi$ find.  type f  print0  xargs 0 perl  pi  e 's/NoXIB/___PROJECTNAME___/g '

; MMHK_CurrentVector  > The direction of the current mouse movement in radians. (a float between  pi & +pi. 0 is left,  pi & +pi is right) #Persistent return

 rwrwrw  1 pi admin 335 27 Aug 15: 50 main. m PiBook: NoXIB pi$ mv NoXIB_Prefix. pch

 > The direction of the current mouse movement in radians. (a float between  pi & +pi.

I have already mentioned that the dwellings of the islanders were almost invariably built upon massive stone foundations, which they call pipis.

You could slice up history into what he called pi cycles, each lasting exactly three thousand one hundred and fortyone days, or 8.6 years.

You will notice that this function is not tail recursive, indeed the last operation to happen in the second branch is not a direct call to fact, but a call to the multiplication operator (*) with arguments n and fact(n  1). (see my article on 1st Class Function to know how to make this function tail recursive) keyword allows you to bind symbol/names to values. for example let pi = 3.14 will bind the value 3.14 to the name pi.

UPDATE: The same quibble applies to the CNN story, which says Mathematicians know that pi is irrational — it cannot be represented as one number divided by another — and transcendental, meaning it is not algebraic.

A proof of the nonexistence of any particular finite sequence of digits in its decimal expansion would have as a corollary that pi is not normal.

OperationCounterstrike: It has been neither proven nor disproven that pi is normal.
dinkum commented on the word pi
WORD: pi (π)
DEFINITION:
(1) In the grand tradition of the supermarket tabloid The National Enquirer, pi (π) is the mathematical constant which, to Kurt Vonnegut's way of thinking, exposes the "secret lives" of circles.
(2) " The number π is a mathematical constant that is the ratio of a circle's circumference to its diameter, and is approximately equal to 3.14159. It has been represented by the Greek letter "π" since the mid18th century, though it is also sometimes written as "pi" (/paɪ/). π is an irrational number, which means that it cannot be expressed exactly as a ratio of any two integers (fractions such as 22/7 are commonly used to approximate π; no fraction can be its exact value); consequently, its decimal representation never ends and never settles into a permanent repeating pattern. The digits appear to be randomly distributed, although no proof of this has yet been discovered. π is a transcendental number – a number that is not the root of any nonzero polynomial having rational coefficients. The transcendence of π implies that it is impossible to solve the ancient challenge of squaring the circle with a compass and straightedge."  Wikipedia
EXAMPLE:
' And now I drew a symbol whose meaning *Dwayne had known for a few years in school, a meaning which had since eluded him. The symbol would have looked like the end of a table in a prison dining hall to *Wayne. It represented the ratio of the circumference of a circle to its diameter. This ratio could also could also be expressed as a number, and even as . . . all the rest of us went about our business, Earthling scientists were monotonously radioing that number into outer space. The idea was to show other inhabited planets, in case they were listening, how intelligent we were. We had tortured circles until they coughed up this symbol of their secret lives:
' pi π '
 From Kurt Vonnegut's 1973 novel Breakfast of Champions  Chapter 19 (page 207).
1973 KURT VONNEGUT, JR. Breakfast of Champions, or, Goodbye Blue Monday.
* NOTE: "Wayne" is not a typo here. "Dwayne" and "Wayne" are two entirely different characters in Vonnegut's novel. Dwayne, for instance, is white, and Wayne is black.
August 28, 2013
jmjarmstrong commented on the word pi
JM wonders if some folk owe their large circumference to too much pi.
May 31, 2011
chained_bear commented on the word pi
Seen here.
December 24, 2008
gangerh commented on the word pi
And then would pi itself be the antidote?
February 17, 2008
gangerh commented on the word pi
Extrapolating my schooltide mathematics I calculate that I could fill all available space on every server on the world wide web with the number represented by this one Greek letter. Now would that be some Trojan Horse?
February 17, 2008
oroboros commented on the word pi
See also:myturtlepanchowillmylovepickupmynewmovergingermame.
October 21, 2007
reesetee commented on the word pi
Yeah, they kind of kill it right there, don't they?
October 6, 2007
seanahan commented on the word pi
I enjoy how Wikipedia explains the Feynman point joke,
"The humorous irony of this statement is the suggestion that..."
Which means that if you've read that far, you're not going to find it funny.
October 6, 2007
uselessness commented on the word pi
So you're a piphilologist, are you?
October 6, 2007
orbitalcombustion commented on the word pi
Beautiful number. Trying to memorize up to Feynman point.
October 6, 2007