z

the obscuring of the light of the moon by the intervention of the earth between it and the sun, a lunar eclipse, or the obscuring of the light of the sun by the intervention of the moon between it and a point on the earth, a solar eclipse

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Astronomy. zenith distance.

zone.

Symbol.

the 26th in order or in a series, or, when I is omitted, the 25th.

(sometimes lowercase) the medieval Roman numeral for 2000. Compare Roman numerals.

Chemistry, Physics. atomic number.

Electricity, impedance.

zone.

Symbol, Mathematics.

an unknown quantity or variable.

(in Cartesian coordinates) the z- axis.

zero.

Symbol, Physics. Z-zero particle.

noun ( used with a plural verb ) Slang.

sleep (often used with grab, catch, etc.): to grab some z's before dinner.

Also, Z's.

Origin:
1960–65; from the conventional use of a series of z's to represent snoring

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Based on the Random House Dictionary, © Random House, Inc. 2013.
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Link To Z

Collins

World English Dictionary

z or Z (zɛd, US ziː, zɛd, US ziː)

—n , pl z's, Z's, Zs
1.	the 26th and last letter and the 20th consonant of the modern English alphabet
2.	a speech sound represented by this letter, in English usually a voiced alveolar fricative, as in zip
3.	a. something shaped like a Z
	b. (in combination): a Z-bend in a road

Z or Z

—n

z or Z (zɛd, US ziː, zɛd, US ziː)

—n , pl z's, Z's, Zs
1.	the 26th and last letter and the 20th consonant of the modern English alphabet
2.	a speech sound represented by this letter, in English usually a voiced alveolar fricative, as in zip
3.	a. something shaped like a Z
	b. (in combination): a Z-bend in a road

Z or Z

—n

z

—*symbol for*
1.	the z-axis or a coordinate measured along the z-axis in a Cartesian or cylindrical coordinate system
2.	an algebraic variable

Z

—*symbol for*
1.	any unknown, variable, or unspecified factor, number, person, or thing
2.	chem atomic number
3.	physics impedance
4.	zone
5.	currency zaïre

—*abbreviation for*
6.	Zambia (international car registration)

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Etymonline

Word Origin & History

not a native letter in O.E.; in Anglo-Fr. words it represents the "ts" sound (cf. Anglo-Fr. fiz, from L. filius, modern Fitz); late 13c. it began to be used for the voiced "s" sound and had fully taken that role by 1400. For letter name, see zed.

"Thou whoreson Zed, thou vnnecessary Letter." ["King Lear," II.ii.69]

Series of zs to represent a buzzing sound first attested 1852; zees "spell of sleep, a nap" is slang first recorded 1963, Amer.Eng. student slang.

FOLDOC

Computing Dictionary

Z definition

/zed/ 1. (After Zermelo-Fränkel set theory) A specification language developed by the Programming Research Group at Oxford University around 1980. Z is used for describing and modelling computing systems. It is based on axiomatic set theory and first order predicate logic. Z is written using many non-ASCII symbols. It was used in the IBM CICS project.
See also Z++.
["Understanding Z", J.M. Spivey, Cambridge U Press 1988].
2. A stack-based, complex arithmetic simulation language from ZOLA Technologies.
(1995-08-11)

American Heritage

Abbreviations & Acronyms