There are 3 main definitions of X in English:


Syllabification: X
(also x)

noun (plural Xs or X's)

1The twenty-fourth letter of the alphabet.
More example sentences
  • X is the 24th letter of the alphabet and it's got me stumped.
  • The Latin X came from Chi, a letter invented by the Greeks who used it to represent the sound ks in the Western part of the country.
1.1Denoting the next after W in a set of items, categories, etc.
More example sentences
  • You give the variable operand one of the 4 names #W, #X, #Y, or #Z.
  • A participant may answer a multiple-choice question with either the letter answer (W, X, Y or Z) or the verbal answer; however, if the verbal answer is given, it must be exactly as indicated in the question.
1.2Denoting an unknown or unspecified person or thing: there is nothing in the data to tell us whether X causes Y or Y causes X
More example sentences
  • Discover how 'Mr X' built an online business making over $100,000 a month (mostly profit) in just 16 weeks.
  • A greater number of fresh vegetables are sold in City X than in City Y.
  • Regarding Mr. X's remarks about the Directorate of Operations' "pitiful management": I did describe in my article the problem of upwardly mobile mediocrity, but Mr. X is right to fault me for not hammering home the point.
1.3 (x) (Used in describing play in bridge) denoting an unspecified card other than an honor.
More example sentences
  • In this case we are comparing the chances of East having J-10-x, J-x, or 10-x.
  • If your doubleton suit is in the form of: K Q, K J, Q J, Q x, J x don't count both honor and Shape points.
1.4 (usually x) The first unknown quantity in an algebraic expression, usually the independent variable.
[the introduction of x, y, and z as symbols of unknown quantities is due to Descartes (Géométrie, 1637), who took z as the first unknown and then proceeded backward in the alphabet]
More example sentences
  • We express a relationship between two variables, which we will refer to as x and y, by stating the following: The value of the variable y depends upon the value of the variable x.
  • For the quadratic function y=X^ - 9, determine the values of X such that y>or equal to 7.
1.5 (usually x) Denoting the principal or horizontal axis in a system of coordinates.
More example sentences
  • When displaying two variables in a time domain plot, the X-axis is labeled with units of time.
  • Click on the Options tab; then choose XY Plot and select the signal to be used for X coordinate generation in the X-Axis box.
2A cross-shaped written symbol, in particular.
2.1Used to indicate a position on a map or diagram.
More example sentences
  • In Sweden, X is used by the armed forces on maps to denote that blasting or other type of destruction has been prepared.
  • If you happen to camp just North of the straight trail section, the only way to accurately place the X on the map is to use a GPS.
  • The students are to use the map to find the sites marked with an X.
2.2Used to indicate a mistake or incorrect answer.
More example sentences
  • Mark incorrect responses with an X.
  • I put a check next to correct problems and an X by incorrect problems.
2.3Used in a letter or message to symbolize a kiss.
More example sentences
  • Have a lovely day! xxxxx
  • Take care, love, Raffa xxx
2.4Used to indicate one’s vote on a paper ballot.
More example sentences
  • In order to vote you simply put an 'X' next to the name of the candidate you support.
  • Voters mark an 'X' in the first column for their first choice and a second 'X' in the second column for their other choice.
2.5Used in place of the signature of a person who cannot write.
More example sentences
  • When a person is physically unable to sign his or her name on the voter registration form, he or she may mark an X or take an oath swearing to the statement on the form.
  • In many jurisdictions testators may authenticate their last will and testament with the letter X
  • In other states the law requires courts to invalidate wills that are signed with an X unless the testator was physically or mentally incapable of signing her full name.
3A shape like that of a letter X: two wires in the form of an X [in combination]: an X-shaped cross
More example sentences
  • The design of the Exofit safety harness uses a single piece of material constructed in the shape of an "X" that wraps around the worker.
  • These conditions are normally very difficult to achieve, but we can reproduce these conditions by using two (or more) fine wires arranged so that they cross and touch at a single point, in the form of an X, as the load of a pulsed power generator.
  • As a compromise, management marked each of the Idles' hands with a large black "X" as a warning to the club's staff not to serve alcohol to the band.
4The Roman numeral for ten.
More example sentences
  • So XXXI is 31, and XXIV is 24.
  • IX means to subtract I from X, leaving 9.
  • These inscriptions allow us to demonstrate the presence of seven cohorts of the legion, either in whole or part, building on Hadrian's Wall: cohorts I, II, III, VI, VII, VIII and X.

verb (X's, X'ing, X'd)

[with object] Back to top  
1Mark or make a sign with an X.
More example sentences
  • Another day X'ed on my calender.
  • Try yellow highlighter X'd on the inside window as one big X or several little X's.
1.1Overwrite or obliterate with an X or series of X’s.
More example sentences
  • There are hand-written notes and corrections, done in pencil; in some places whole blocks of text are stricken out, x'd over with a typewriter or opaqued with red crayon.
  • Also can he go to court and say that the XXX'd over paragraphs are still valid?
1.2Make void or annul; invalidate: we’re all X-ing things out of our curricula
More example sentences
  • Uh, I found more but then accidentally Xed out the page and I'm too lazy to bring it back up.
  • X is for X-ing out accidents in your home.
  • We're talking about a savings of some $20 million per year alone just by x-ing out this non-essential department completely.

Definition of X in:

There are 3 main definitions of X in English:


Line breaks: X

Entry from British & World English dictionary


North American informal
The drug Ecstasy.

Definition of X in: