noun, often capitalized, often attributive
\ ˈeks How to pronounce x (audio) \
plural x's or xs\ ˈek-​səz How to pronounce x (audio) \

Definition of x

 (Entry 1 of 5)

1a : the 24th letter of the English alphabet
b : a graphic representation of this letter
c : a speech counterpart of orthographic x
2 : ten — see Table of Numbers
3 : a graphic device for reproducing the letter x
4 : one designated x especially as the 24th in order or class, or the first in an order or class that includes x, y, and sometimes z
5 : an unknown quantity
6 : something shaped like or marked with the letter X


x-ed also x'd or xed\ ˈekst How to pronounce x (audio) \; x-ing or x'ing\ ˈek-​siŋ How to pronounce x (audio) \

Definition of x (Entry 2 of 5)

transitive verb

1 : to mark with an x
2 : to cancel or obliterate with a series of x's usually used with out x-ed out the mistake

Definition of x (Entry 3 of 5)

1 cross
2 ex
3 experimental
4 extra



Definition of x (Entry 4 of 5)

1a times 2 x 3 = 6 The picture was enlarged 3x [=enlarged to three times the original size].
b by used in measurements an 8x11 sheet of paperAn early 20th century Persian Hamadan Gallery carpet with a camel hair ground, measuring 10.10 x 5.5.The Magazine Antiques
2 by used in nonmathematical constructions He drove a 4x4 vehicle.
\ ˈeks How to pronounce X (audio) \

Definition of X (Entry 5 of 5)

of a motion picture
: of such a nature that admission is denied to persons under a specified age (such as 17) used before the adoption of NC-17

Words Starting With X

Browse 436 words and phrases that start with the letter X, from Xanadu to xystus.

Examples of x in a Sentence

Noun a word that starts with an x a word that starts with x

First Known Use of x


before the 12th century, in the meaning defined at sense 1a


circa 1849, in the meaning defined at sense 1


1970, in the meaning defined above

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The first known use of x was before the 12th century

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Last Updated

15 Apr 2022

Cite this Entry

“X.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/x. Accessed 24 May. 2022.

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More Definitions for x


noun, often capitalized
\ ˈeks How to pronounce x (audio) \
plural x's or xs\ ˈek-​səz \

Kids Definition of x

1 : the 24th letter of the English alphabet
2 : ten in Roman numerals
3 : an unknown quantity What is the value of x in the equation x + 2 = 6?


\ ˈeks How to pronounce x (audio) \
plural x's or xs or x'es or xes\ ˈek-​səz How to pronounce x (audio) \

Medical Definition of x

 (Entry 1 of 2)

: the basic or monoploid number of chromosomes of a polyploid series : the number contained in a single genome — compare n sense 1



Medical Definition of x (Entry 2 of 2)

1 capitalized halogen atom used in general formulas (as of trihalomethane CHX3)
2 power of magnification


noun, often capitalized
\ ˈeks How to pronounce x (audio) \

Legal Definition of x

 (Entry 1 of 2)

1 : a mark used in place of a signature when the maker is incapable of signing his or her name (as because of illiteracy or a physical ailment)
2 : a mark used in indicating a choice or applicable item (as on an insurance form)



Legal Definition of x (Entry 2 of 2)

1 ex-distribution
2 ex-dividend
3 ex-rights
4 ex-warrants

More from Merriam-Webster on x

Nglish: Translation of x for Spanish Speakers

Britannica.com: Encyclopedia article about x


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