mast

¹ American  

[mast, mahst] / mæst, mɑst /

noun

1. Nautical.

   1. a spar or structure rising above the hull and upper portions of a ship or boat to hold sails, spars, rigging, booms, signals, etc., at some point on the fore-and-aft line, as a foremast or mainmast.

   2. any of a number of individual spars composing such a structure, as a topmast supported on trestletrees at the head of a lower mast.

   3. any of various portions of a single spar that are beside particular sails, as a top-gallant mast and royal mast formed as a single spar.

2. Also called pillar.  the upright support of a jib crane.

3. any upright pole, as a support for an aerial, a post in certain cranes, etc.

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verb (used with object)

1. to provide with a mast or masts.

idioms

1. before the mast, as an unlicensed sailor.

   He served several years before the mast.

mast ² American  

[mast, mahst] / mæst, mɑst /

noun

1. the fruit of the oak and beech or other forest trees, used as food for hogs and other animals.

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mast- ³ American  

1. variant of masto- before a vowel.

   mastectomy.

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mast ¹ British  

/ mɑːst /

noun

1. nautical any vertical spar for supporting sails, rigging, flags, etc, above the deck of a vessel or any components of such a composite spar

2. any sturdy upright pole used as a support

3. Also called: captain's mast.  nautical a hearing conducted by the captain of a vessel into minor offences of the crew

4. nautical as an apprentice seaman

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verb

1. (tr) nautical to equip with a mast or masts

mast ² British  

/ mɑːst /

noun

1. the fruit of forest trees, such as beech, oak, etc, used as food for pigs

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mast- ³ British  

combining form

1. a variant of masto-

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mast More Idioms  

1. see at half-mast.

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Usage

What does mast- mean? Mast- is a combining form used like a prefix meaning “breast.” It is often used in medical terms, especially in anatomy and pathology. Mast- comes from the Greek mastós, meaning “breast.” The Latin-based analog to masto- is mammo-, from mamma, meaning “breast.”Mast- is a variant of masto-, which loses its -o- when combined with words or word elements beginning with vowels. Want to know more? Read our Words That Use masto- article.

Other Word Forms

• mastless adjective
• mastlike adjective
• undermasted adjective

Etymology

Origin of mast¹

First recorded before 900; Middle English; Old English mæst; cognate with Dutch mast, German Mast; akin to Latin mālus “pole”

Origin of mast²

First recorded before 900; Middle English; Old English mæst; cognate with German Mast “food”; akin to meat

Explanation

A mast is a pole that rises vertically from a ship and supports the sails. Really big sailboats have more than one mast. A mast is also another name for flagpole. The mast has an important job — to support the sails, which allows the wind to propel the ship. Other types of masts are used to support flags and called flagpoles. If you've ever seen a flag at half-mast, it's been lowered down the flagpole to show respect for someone who died. Mast is an old word meaning “pole or rod.”

Example Sentences

The Fed didn’t always nail its colors to a predictive mast.

From The Wall Street Journal • Mar. 26, 2026

There are fun house mirrors, a whimsical train, a mechanical Geppetto waving in a workshop and a cat ready to set sail atop the mast of a ship.

From Los Angeles Times • Jan. 21, 2026

The device operates like a mobile phone mast in space, using a constellation of satellites to communicate with small dishes on the ground with a built-in WiFi router.

From BBC • Jan. 14, 2026

Swiss President Guy Parmelin, who took over on Thursday, called the fire "a calamity of unprecedented, terrifying proportions", and announced that flags would be flown at half mast for five days.

From Barron's • Jan. 2, 2026

Its head was level with Christopher’s as he stood with his back against the boat’s mast.

From "Impossible Creatures" by Katherine Rundell

Related Words

• pole