horizontal

adjective

hor·​i·​zon·​tal ˌhȯr-ə-ˈzän-tᵊl How to pronounce horizontal (audio)
ˌhär-
Synonyms of horizontal
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 How to pronounce horizontal (audio)
ˌhär-
noun
horizontally
ˌhȯr-ə-ˈzän-tᵊl-ē How to pronounce horizontal (audio)
ˌhär-
adverb

Examples of horizontal in a Sentence

Recent Examples on the Web
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
The goal was to create labs that were horizontal in structure—meaning they aren’t created or dictated by leadership but by professors—and that incorporated not just teachers and students but alumni as well. — Shanti Escalante-De Mattei, ARTnews.com, 3 Aug. 2026 While the horizontal space in a small garden is defined and limited, the vertical space offers great planting potential. — Megan Hughes, Better Homes & Gardens, 2 Aug. 2026 The actual Texas state flag was established in 1839, with one vertical blue stripe featuring a Lone Star and two horizontal stripes of white and red. — Ella Gonzales, Fort Worth Star-Telegram, 31 July 2026 For much of the past few seasons, sweepers — essentially, bigger sliders with massive horizontal movement — were en vogue. — Cody Stavenhagen, New York Times, 31 July 2026 See All Example Sentences for horizontal

Word History

Etymology

see horizon

First Known Use

1555, in the meaning defined at sense 1a

Time Traveler
The first known use of horizontal was in 1555

Phrases Containing horizontal

Rhymes for horizontal

See All Rhymes for horizontal

Browse Nearby Words

horizon system of coordinates
horizontal
horizontal bar
See all Nearby Words

Cite this Entry

“Horizontal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/horizontal. Accessed 5 Aug. 2026.

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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- How to pronounce horizontal (audio)
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 How to pronounce horizontal (audio)
adverb

Legal Definition

horizontal

adjective
hor·​i·​zon·​tal ˌhȯr-ə-ˈzän-təl, ˌhär- How to pronounce horizontal (audio)
: relating to, directed toward, or consisting of individuals or entities of similar status or on the same level
horizontally adverb
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