pi

Etymology 1

From Ancient Greek πεῖ (peî), ultimately from Proto-Semitic *pay- (“mouth”). Doublet of pe. Its mathematical use apparently stems from its use as the first letter in περιφέρεια (periphéreia, “periphery; circumference”) and was first cited in 1706 in the Synopsis Palmariorum Matheseos by William Jones.

noun

1. The 16th letter of the Classical and Modern Greek alphabets and the seventeenth in Old Greek.
2. (mathematics) An irrational and transcendental constant representing the ratio of the circumference of a Euclidean circle to its diameter; approximately 3.14159265358979323846264338327950; usually written π.
3. (letterpress typography) Metal type that has been spilled, mixed together, or disordered.

verb

1. (letterpress typography) To spill or mix printing type.

adj

1. (typography) Not part of the usual font character set; especially, non-Roman type or symbols as opposed to standard alphanumeric Roman type.
   In computing, pi characters may be entered with special key combinations.

Etymology 2

Abbreviations.

noun

1. (typography) pica (conventionally, 12 points = 1 pica, 6 picas ≈ 1 inch).
2. Piaster.

adj

1. Pious.
   Our Major was "Cherub" Cheeseman, noted for his foul language. I am afraid he lost a tidy little legacy that he was expecting from his aunt, the Dowager Lady Shuttlecock (a very "pi" old lady), through this same habit of his. 1927, Magdalen King-Hall, I Think I Remember: Being the Random Recollections of Sir Wickham Woolicomb, an Ordinary English Snob and Gentleman
   “Those are very 'pi' sentiments. Was a preacher in Staffordshire— I was raised chapel, though've tried to forget it—he talked that way... redemption and the lot.” 1972, Anya Seton, Green Darkness, Hachette UK
   In Sense and Sensibility, as even you might agree, there's at least the danger of a rather pi moral framework clamping down on the spontaneous fun and leaving the sisters to survive - a bit drearily - on the periphery of a mean world. 1994, Roger Gard, Jane Austen's Novels: The Art of Clarity, Yale University Press, page 101