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• mast
  mast

  noun
• mast-
  mast-

  variant of masto- before a vowel.

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

Derived Forms

• undermasted
  adjective
• mastless
  adjective
• mastlike
  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

Mast cells appear to have evolved from macrophages, while early versions of T cells and red blood cells later emerged from mast cells.

From Science Daily • May 27, 2026

“Silver has deviated from its linkages to gold and other precious metals,” said Yung-Shin Kung, chief investment officer of Mast Investments.

From Barron's • Jan. 9, 2026

Sharaa met Sunday night in Washington with Rep. Brian Mast, the Republican chairman of the House Foreign Affairs Committee, who has been one of the last holdouts in Congress in repealing that 2019 legislation.

From The Wall Street Journal • Nov. 10, 2025

Committee Chairman Brian Mast, R-Fla., ceded his remaining time to Lake, who used it to claim that VOA had not “told the story of America properly or positively.”

From Salon • Jun. 25, 2025

At Ewa Mooring Mast Field, a technical sergeant was peering through the lens of a camera at his three-year-old son.

From "Unbroken" by Laura Hillenbrand

Related Words

• pole