horizontal

1 of 2

adjective

hor·​i·​zon·​tal ˌhȯr-ə-ˈzän-tᵊl 

ˌhär-

1

a

: of or relating to the apparent junction of earth and sky : situated near the horizon

b

: parallel to, in the plane of, or operating in a plane parallel to the horizon or to a baseline : level

horizontal distance

a horizontal engine

2

: relating to, directed toward, or consisting of individuals or entities of similar status or on the same level

horizontal mergers

horizontal hostility

3

medical : relating to or being transmission (as of a disease) by physical contact or proximity in contrast with inheritance

horizontal transmission of the hepatitis B virus

Genes are normally inherited from parents, but they can also be inserted into a genome by viruses, plasmids, and other foreign agents—a phenomenon called horizontal transfer.

—Stephan Reebs

compare vertical sense 4

horizontal noun

horizontality

ˌhȯr-ə-ˌzän-ˈta-lə-tē 

ˌhär-

noun

horizontally

ˌhȯr-ə-ˈzän-tᵊl-ē 

ˌhär-

adverb

horizontality

2 of 2

noun

hor·​i·​zon·​tal·​i·​ty ˌhȯrəˌzän‧ˈtȧlətē 

ˌhär-

plural -es

: the quality or state of being horizontal

his houses have a pronounced horizontality

—J. M. Richards

Examples of horizontal in a Sentence

Recent Examples on the Web

Adjective

In fact, the tapestry’s most singular attribute is its luxurious use of horizontal space. — John Phipps, New Yorker, 5 Sep. 2026

Scheduled for late 2026, Ceres will drill the world’s first commercial-scale superhot horizontal wells, bringing subterranean power one step closer to the grid. — Mrigakshi Dixit, Interesting Engineering, 4 Sep. 2026

The curved trees were then placed on a horizontal rotating platform inside a sphere lit up from every direction. — New Atlas, 4 Sep. 2026

Larger configurations, such as the R140X, incorporate swiveling crossbars with snap locks alongside vertical and horizontal dividers for customized interior partitioning. — IEEE Spectrum, 3 Sep. 2026

Word History

Etymology

Adjective

see horizon

First Known Use

Adjective

1555, in the meaning defined at sense 1a

Phrases Containing horizontal

• horizontal bar

Rhymes for horizontal

• consonantal
• periodontal
• quantal

Kids Definition

horizontal

1 of 2 adjective

hor·​i·​zon·​tal

ˌhȯr-ə-ˈzänt-ᵊl, 

ˌhär-

1

: of or relating to the horizon

2

: parallel to the horizon : level

3

: being on the same level

horizontally

-ᵊl-ē

adverb

horizontal

2 of 2 noun

: a horizontal line or plane

Medical Definition

horizontal

adjective

hor·​i·​zon·​tal ˌhȯr-ə-ˈzänt-ᵊl, ˌhär- 

1

: relating to or being a transverse plane or section of the body

2

a

: relating to or being transmission (as of a disease) by physical contact or proximity in contrast with inheritance compare vertical

b

: of or relating to horizontal gene transfer

horizontally

-ᵊl-ē 

adverb

Legal Definition

horizontal

adjective

hor·​i·​zon·​tal ˌhȯr-ə-ˈzän-təl, ˌhär- 

: relating to, directed toward, or consisting of individuals or entities of similar status or on the same level

horizontally adverb