horizontal

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

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

Examples of horizontal in a Sentence

Recent Examples on the Web

The Grammy Award-winning artist styled a pair of loose-fitting black jeans with coordinated flats and a Balenciaga polo in a base shade of blue with black and faint pink horizontal stripes. —Julia Teti, Footwear News, 22 Apr. 2025

That battery-electric, four-passenger aircraft will take off and land vertically, then transition to horizontal flight at speeds of up to 150mph. —Rob Pegoraro, PC Magazine, 17 Apr. 2025

Investigators have recovered the helicopter’s main fuselage, including its cockpit and cabin, the forward portion of its tail boom, its horizontal stabilizer finlets and its vertical fin, the safety board announced Saturday night. —John Annese, New York Daily News, 13 Apr. 2025

New York City helicopter crash latest: Authorities search for answers after 6 killed The main fuselage, including the cockpit and cabin, the forward portion of the tail boom, the horizontal stabilizer finlets and the vertical fin have all been recovered, according to the agency. —Riley Hoffman, ABC News, 12 Apr. 2025

Word History

Etymology

see horizon

First Known Use

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