X, x

[eks]
noun, plural X's or Xs, x's or xs.
1.
the 24th letter of the English alphabet, a consonant.
2.
any spoken sound or combination of sounds represented by the letter X or x, as in xylene, box, or exact.
3.
something having the shape of an X .
4.
a written or printed representation of the letter X or x.
5.
a device, as a printer's type, for reproducing the letter X or x.
Dictionary.com Unabridged

x

[eks]
verb (used with object), x-ed or x'd [ekst] , x-ing or x'ing [ek-sing] .
1.
to cross out or mark with or as if with an x (often followed by out ): to x out an error.
2.
to indicate choice, as on a ballot or examination (often followed by in ): to x in the candidate of your choice.

Origin:
1840–50

X

Symbol.
1.
the 24th in order or in a series, or, when I is omitted, the 23rd.
2.
(sometimes lowercase) the Roman numeral for 10. Compare Roman numerals.
6.
Electricity, reactance.
7.
Slang. a ten-dollar bill.
8.
(in the U.S.) a rating of the Motion Picture Association of America for movies with subject matter that is suitable for adults only: persons who are under age (usually 17) will not be admitted. Compare G ( def 7 ), PG, PG-13, See R ( def 5 ).
9.
(in Great Britain) a designation for a film recommended for adults only. Compare A ( def 11 ), AA ( def 5 ), U ( def 5 ).
10.
a person, thing, agency, factor, etc., of unknown identity.
11.
Chemistry. (formerly) xenon.

x

1.
ex1 ( def 1 ).
3.
Stock Exchange.
a.
(of stock trading) ex dividend.
b.
(of bond trading) ex interest.

x

Symbol.
1.
an unknown quantity or a variable.
2.
(used at the end of letters, telegrams, etc., to indicate a kiss.)
3.
(used to indicate multiplication) times: 8 × 8=64.
4.
(used between figures indicating dimensions) by: 3″ × 4″ (read: “three by four inches”); 3″ × 4″ × 5″ (read: “three by four by five inches”).
5.
power of magnification: a 50x telescope.
6.
(used as a signature by an illiterate person.)
8.
crossed with.
9.
(used to indicate a particular place or point on a map or diagram.)
10.
out of; foaled by: a colt by Flag-a-way x Merrylegs.
11.
(used to indicate choice, as on a ballot, examination, etc.)
12.
(used to indicate an error or incorrect answer, as on a test.)
13.
Mathematics. (in Cartesian coordinates) the x-axis.
14.
Chess. captures.
15.
a person, thing, agency, factor, etc., of unknown identity.
Dictionary.com Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2014.
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Collins
World English Dictionary
x or X (ɛks)
 
n , pl x's, X's, Xs
1.  the 24th letter and 19th consonant of the modern English alphabet
2.  a speech sound sequence represented by this letter, in English pronounced as ks or gz or, in initial position, z, as in xylophone
 
X or X
 
n

x
 
symbol for
1.  commerce, banking, finance ex
2.  maths the x-axis or a coordinate measured along the x-axis in a Cartesian coordinate system
3.  an algebraic variable

X
 
symbol for
1.  formerly, in Britain
 a.  indicating a film that may not be publicly shown to anyone under 18. Since 1982 replaced by symbol 18
 b.  (as modifier): an X film
2.  denoting any unknown, unspecified, or variable factor, number, person, or thing
3.  (on letters, cards, etc) denoting a kiss
4.  (on ballot papers, etc) indicating choice
5.  (on examination papers, etc) indicating error
6.  for Christ; Christian
7.  Roman numeral See Roman numerals ten
 
[(sense 6) from the form of the Greek letter khi (Χ), first letter of Khristos Christ]

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

X
most Eng. words beginning in -x- are of Gk. origin or modern commercial coinages. E. Anglian in 14c. showed a tendency to use -x- for initial sh-, sch- (cf. xal for shall), which didn't catch on but seems an improvement over the current system. As a symbol of a kiss on a letter, etc., it is recorded
from 1765. In malt liquor, XX denoted "double quality" and XXX "strongest quality" (1827). Algebraic meaning "unknown quantity" (1660 in Eng.), sometimes said to be from medieval use, originally a crossed -r-, probably from L. radix (see root). Other theories trace it to Arabic, but a more prosaic explanation says Descartes (1637) took x, y, z, the last three letters of the alphabet, for unknowns to correspond to a, b, c, used for known quantities. Used allusively for "unknown person" from 1797, "something unknown" since 1859. As a type of chromosome, attested from 1902. First used 1950 in Britain to designate "films deemed suitable for adults only;" adopted in U.S. Nov. 1, 1968.
Online Etymology Dictionary, © 2010 Douglas Harper
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FOLDOC
Computing Dictionary

X definition


1. Used in various speech and writing contexts (also in lowercase) in roughly its algebraic sense of "unknown within a set defined by context" (compare N). Thus, the abbreviation 680x0 stands for 68000, 68010, 68020, 68030 or 68040, and 80x86 stands for Intel 80186, Intel 80286, Intel 80386 or Intel 80486. A Unix hacker might write these as 680[0-4]0 and 80[1-4]86 or 680?0 and 80?86 respectively; see glob.
2. An alternative name for the X Window System.
3. A suffix for the speed of a CD-ROM drive relative to standard music CDs (1x). 32x is common in September 1999.
[Jargon File]
(1999-09-15)

The Free On-line Dictionary of Computing, © Denis Howe 2010 http://foldoc.org
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American Heritage
Abbreviations & Acronyms
x
  1. abscissa

  2. by

  3. times (that is, multiplication)

X
  1. adult audiences only

  2. Christ

  3. Christian

  4. experimental

  5. extra

  6. reactance

  7. 10

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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Encyclopedia Britannica
Encyclopedia

x

American band whose tales of urban decay, corruption, and sleaze, delivered with skilled musicianship and unique vocal harmonies, marked them as important contributors to the punk movement. The original members were Exene Cervenka (original name Christine Cervenka; b. Feb. 1, 1956, Chicago, Ill., U.S., ), John Doe (b. Feb. 25, 1953, Decatur, Ill., ), Billy Zoom (original name Ty Kindell; b. Feb. 20, 1948, Illinois, ), and D.J. Bonebrake (b. Dec. 8, 1955, North Hollywood, Calif., ). Later members included Dave Alvin (b. Nov. 11, 1955, Los Angeles, Calif., ) and Tony Gilkyson.

Learn more about X with a free trial on Britannica.com.

Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences for x
This is because ss was written with a ligature closely resembling the x.
He has covered several songs of hers, including the controversial rated x.
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