A horizon

[ eyhuh-rahy-zuhn ]

/ ˈeɪ həˌraɪ zən /

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noun Geology.

the topsoil in a soil profile.

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Also called zone of leaching .

Compare B horizon, C horizon.

Origin of A horizon

First recorded in 1935–40

Words nearby A horizon

ahold, a-hole, -aholic, aholt, Ahom, A horizon, ahorse, horse of a different color, a, ahoy, AHQ, AHRA

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022

How to use A horizon in a sentence

ROME — What does it take for a Hollywood A-lister to get a private audience with Pope Francis?
Pope Francis Has the Pleasure of Meeting Angelina Jolie for a Few Seconds|Barbie Latza Nadeau|January 8, 2015|DAILY BEAST
Yes, Byrd—dead four-and-a-half years now—was a Kleagle in the Ku Klux Klan.
Steve Scalise and the Right’s Ridiculous Racial Blame Game|Michael Tomasky|January 2, 2015|DAILY BEAST
But without any peace talks on the horizon, everyone is now left to their own devices.
In the Middle East, the Two-State Solution Is Dead|Dean Obeidallah|January 2, 2015|DAILY BEAST
By the time it concluded with a sing-a-long of “XO,” Beyoncé had done the rare thing.
Bow Down, Bitches: How Beyoncé Turned an Elevator Brawl Into a Perfect Year|Kevin Fallon|December 31, 2014|DAILY BEAST

In another year, stories about the strange new face of an A-list actress might draw chortles and cackles.
Renée Zellweger Got a New Face—and Everyone Had An Opinion About It|Kevin O’Keeffe|December 29, 2014|DAILY BEAST
Now-a-days it is the bankrupt who flouts, and his too confiding creditors who are jeered and laughed at.
Glances at Europe|Horace Greeley
He felt himself the meanest, vilest thing a-crawl upon this sinful earth, and she—dear God!
St. Martin's Summer|Rafael Sabatini
All that scientific bric-a-brac in the cupboard had far better be thrown away.
The Salvaging Of Civilisation|H. G. (Herbert George) Wells
See how those distant peaks rise serenely over the southern horizon!
Blackwood's Edinburgh Magazine, Volume 60, No. 372, October 1846|Various
Urinary sediments may be studied under three heads: A. Unorganized sediments.
A Manual of Clinical Diagnosis|James Campbell Todd

British Dictionary definitions for A horizon

A horizon

noun

the top layer of a soil profile, usually dark-coloured and containing humus and from which soluble salts may have been leachedSee B horizon, C horizon

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Scientific definitions for A horizon

A horizon

In ABC soil, the uppermost, darkest zone that is rich in organic matter. The upper section of the A horizon usually contains humus along with plant and animal matter in varying stages of decay. The middle section usually contains a high concentration of quartz or other minerals that remain following the leaching away of clay, iron, and aluminum. The lower section is typically transitional in nature between the A horizon and the B horizon. Also called zone of leaching