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PI

UK:**UK and possibly other pronunciationsUK and possibly other pronunciations/paɪ/US:USA pronunciation: IPA and respellingUSA pronunciation: IPA/paɪ/ ,USA pronunciation: respelling(pī)

Inflections of 'pi' (n):
pis
npl (For the Greek letter and mathematical sense)
pies
npl (For the printing sense)
Inflections of 'pi' (v): (⇒ conjugate)
pies
v 3rd person singular
piing
v pres p
pied
v past
pied
v past p

Collins Concise English Dictionary © HarperCollins Publishers::
PI abbreviation for
  1. Philippine Islands
  2. private investigator
WordReference Random House Learner's Dictionary of American English © 2026
pi1 /paɪ/USA pronunciation   n. [countable], pl. pis. 
  1. Linguisticsthe 16th letter of the Greek alphabet (&Pgr;, π).
  2. Mathematics
    • the letter π, used as the symbol for the ratio of the circumference of a circle to its diameter.
    • the ratio itself, a number usually given as 3.141592+.

WordReference Random House Unabridged Dictionary of American English © 2026
pi1  (pī),USA pronunciation n., pl. pis. 
  1. Linguisticsthe 16th letter of the Greek alphabet (II, π).
  2. Linguisticsthe consonant sound represented by this letter.
  3. Mathematics
    • the letter π, used as the symbol for the ratio of the circumference of a circle to its diameter.
    • the ratio itself: 3.141592+.
  • Greek pî, peî; used in mathematics to represent Greek periphérion periphery
  • 1835–45

pi2  (pī),USA pronunciation n., pl. pies, v., pied, pi•ing. 
n. 
  1. Printingprinting types mixed together indiscriminately.
  2. any confused mixture;
    jumble.

v.t. 
  1. Printingto reduce (printing types) to a state of confusion.
  2. to jumble.
Also, pie. 
  • origin, originally uncertain 1650–60

PI, 
    1. Lawpersonal injury.
    2. principal investigator.
    3. private investigator.

Pi., 
  1. piaster.
Also, pi. 
P.I., 
    1. Place NamesPhilippine Islands.
    2. Also, p.i. private investigator.

Collins Concise English Dictionary © HarperCollins Publishers::
pi /paɪ/ n ( pl pis)
  1. the 16th letter in the Greek alphabet (Π, π), a consonant, transliterated as p
  2. 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
Etymology: 18th Century (mathematical use): representing the first letter of Greek periphereia periphery
pi, pie /paɪ/ n ( pl pies)
  1. a jumbled pile of printer's type
  2. a jumbled mixture
 vb (pies, piing, pied, pies, pieing, pied) (transitive)
  1. to spill and mix (set type) indiscriminately
  2. to mix up
Etymology: 17th Century: of uncertain origin
pi /paɪ/ adj
  1. Brit slang
    short for pious, pious
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'PI' also found in these entries (note: many are not synonyms or translations):
bupivacaine - carpus - hippocampus - Hopi - impi - Lee - metacarpus - okapi - pi-dog - pie - pi meson - pion - pithecanthropus - polypus - Powell - pye-dog - streptocarpus - tant pis - tempo - tenuis - tepee - Tupi - air piracy - Antoninus Pius - auction pinochle - automatic pilot - band-tailed pigeon - bush pilot - carpometacarpus - coast pilot - colada - commercial pilot - cow pilot - desiderative - em pica - encarpus - euripus - haloperidol - happi coat - hinoki cypress - homing pigeon - koppa - Leaning Tower of Pisa, The - Life on the Mississippi - loperamide - López de Legazpe - lupus - meperidine - Naskapi - octopus

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