horizontal

adjective

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
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

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.
These stand-alone units use a horizontal form factor to cast sound with better volume and separation. K. Thor Jensen, PC Magazine, 31 Mar. 2025 The San Diego-area man climbed onto a horizontal tree branch and tried to jump from the limb but slipped and then hit his head on the rocks below, the station reported. Anna Lazarus Caplan, People.com, 31 Mar. 2025 Meister can often immediately identify on an MRI that a pitcher throws a sweeper—a hard slider that the pitcher whips to get about fifteen inches of horizontal movement from the ball. Lindsey Adler, New Yorker, 30 Mar. 2025 Against the White Sox, the curveball averaged 10 inches of horizontal movement. Justice Delos Santos, Mercury News, 28 Mar. 2025 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

Cite this Entry

“Horizontal.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/horizontal. Accessed 4 Apr. 2025.

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
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

Legal Definition

horizontal

adjective
: relating to, directed toward, or consisting of individuals or entities of similar status or on the same level
horizontally adverb
Last Updated: - Updated example sentences
Love words? Need even more definitions?

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