x

1 of 5

noun

ˈeks 

plural x's or xs ˈek-səz 

often capitalized, often attributive

1

a

: 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

2 of 5

verb

x-ed also x'd or xed ˈekst  ; x-ing or x'ing ˈek-siŋ 

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

x

3 of 5

abbreviation

1

cross

2

ex

3

experimental

4

extra

x

4 of 5

symbol

1

a

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 paper

An 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.

X

5 of 5

adjective

ˈeks 

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

Did you know?

Words Starting With X

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

Synonyms

Verb

• delete
• cross (out)
• edit (out)
• stroke (out)
• strike (out)
• scratch (out)

Examples of x in a Sentence

Noun

a word that starts with an x

a word that starts with x

Verb

x out the names of the people who have already left

Recent Examples on the Web

Verb

Huntr/x is returning to movie theaters near you. —Rebecca Rubin, Variety, 15 Oct. 2025

The real heroes, however, were the Michelin Pilot Sport Cup 2 tires that were x-rayed before fitment to ensure perfect structural integrity. —Ben Oliver, Robb Report, 30 Sep. 2025

Gap x Béis Denim Travel Backpack Your new go-to travel backpack just dropped, and per Mitchell’s unique design instruction, it’s made of a soft yet durable denim material that’ll hold up well through everything on your itinerary. —Merrell Readman, Travel + Leisure, 5 Aug. 2025

Word History

First Known Use

Noun

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

Verb

circa 1849, in the meaning defined at sense 1

Adjective

1970, in the meaning defined above

Phrases Containing x

• x-axis
• x-coordinate
• x-height
• x-intercept
• x-irradiation
• x out
• x-radiation
• x-ray
• x-section

Kids Definition

x

1 of 3 noun

ˈeks 

often capitalized

1

: the 24th letter of the English alphabet

2

: ten in Roman numerals

3

: an unknown quantity

x

2 of 3 verb

x-ed also x'd or xed ˈekst  ; x-ing or x'ing ˈek-siŋ 

1

: to mark with an x

2

: to cancel with a series of x's

X

3 of 3 adjective

ˈeks 

of a motion picture

: of such a nature that admission is denied to persons under a certain age (as 17)

—used before the adoption of NC-17

Medical Definition

x

1 of 2 noun

ˈeks 

plural x's or xs or x'es or xes ˈek-səz 

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

x

2 of 2 symbol

1

capitalized halogen atom

—used in general formulas (as of trihalomethane CHX₃)

2

power of magnification

Legal Definition

x

1 of 2 noun

ˈeks 

often capitalized

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)

x

2 of 2 abbreviation

1

ex-distribution

2

ex-dividend

3

ex-rights

4

ex-warrants