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

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

Keep scrolling for more

Learn More about x

Time Traveler for x

Time Traveler

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

See more words from the same century

Statistics for x

Cite this Entry

“X.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/x. Accessed 9 May. 2021.

Style: MLA
MLACheck Mark Icon ChicagoCheck Mark Icon APACheck Mark Icon Merriam-WebsterCheck Mark Icon

Keep scrolling for more

More Definitions for x



English Language Learners Definition of x

: the 24th letter of the English alphabet
: the Roman numeral that means 10
used to represent an unknown quantity


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

Keep scrolling for more


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

Comments on x

What made you want to look up x? Please tell us where you read or heard it (including the quote, if possible).


Test Your Vocabulary

Star Wars Words Quiz

  • cu jedi training
  • The bounty portion of bounty hunters (such as Boba Fett) comes from a Latin word meaning
True or False

Test your knowledge - and maybe learn something along the way.


Anagram puzzles meet word search.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!