mare

¹ American  

[mair] / mɛər /

noun

1. a fully mature female horse or other equine animal.

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mare ² American  

[mair] / mɛər /

noun

Obsolete.

1. nightmare.

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mare ³ American  

[mahr-ey, mair-ee] / ˈmɑr eɪ, ˈmɛər i /

noun

Astronomy.

plural

maria

1. any of the several large, dark plains on the moon and Mars: Galileo believed that the lunar features were seas when he first saw them through a telescope.

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mare ¹ British  

/ ˈmɑːreɪ, -rɪ /

noun

1. (capital when part of a name) any of a large number of huge dry plains on the surface of the moon, visible as dark markings and once thought to be seas: Mare Imbrium ( Sea of Showers )

2. a similar area on the surface of Mars, such as Mare Sirenum

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mare ² British  

/ mɛə /

noun

1. the adult female of a horse or zebra

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mare Scientific  

/ mä′rā /

plural

maria

1. Any of the large, low-lying dark areas on the Moon or on Mars or other inner planets. The lunar maria are believed to consist of volcanic basalts, and many are believed to be basins formed initially by large impacts with meteoroids and later filled with lava flows.

2. Compare terra

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Etymology

Origin of mare¹

First recorded before 900; Middle English, mere, mare, maire “horse for riding; beast of burden,” Old English mere, myre “mare”; cognate with Old Frisian merie, Dutch merrie, German Mähre, Old Norse merr; the feminine equivalents to Old English mearh, Old High German marah, march, Old Norse marr, Irish marc, “horse, steed”; marshal

Origin of mare²

First recorded before 900; Middle English mare “night goblin; incubus,” Old English mære, mare, mere “nightmare; monster that oppresses people in their sleep”; cognate with German Mahre, Old Norse mara; nightmare

Origin of mare³

First recorded in 1760–70; from Latin: literally, “sea”

Explanation

A mare is an adult female horse. If your new horse is a filly, a female baby horse, she'll grow up to be a mare. Horse experts have many words to distinguish the age and sex of their animals, from foal, for any newborn horse, to stallion, a full grown male, to colt, a young male horse. Mares are known for being more easy-going than stallions, and because they're equally fast and powerful, they're as likely as males to be used for racing. Another meaning of mare ("sea" in Latin) is "dark areas of the moon," once believed to be actual oceans.

Example Sentences

John: Quite a wonderful, enthusiastic mare who has enjoyed a great season similar to that of Haiti Couleurs.

From BBC • Apr. 9, 2026

Another class of landforms, small mare ridges, has also been identified.

From Science Daily • Feb. 18, 2026

In 2004 former Japanese Prime Minister Junichiro Koizumi even expressed his support for the mare.

From Los Angeles Times • Sep. 9, 2025

If the question is whether the network has declined relative to its own peak performance, then, sure, the old gray mare ain’t what she used to be.

From Slate • May 15, 2024

In a little while, he returned to his alley stable where he had left his rented horse, a bay mare.

From "Chasing Lincoln's Killer" by James L. Swanson

Related Words

• colt
• filly
• stallion