auxiliary

American  

[awg-zil-yuh-ree, -zil-uh-] / ɔgˈzɪl yə ri, -ˈzɪl ə- /

adjective

1. additional; supplementary; reserve.

   an auxiliary police force.

2. used as a substitute or reserve in case of need.

   The hospital has an auxiliary power system in case of a blackout.

   Synonyms:

   secondary, ancillary, backup

3. (of a boat) having an engine that can be used to supplement the sails.

   an auxiliary yawl.

4. giving support; serving as an aid; helpful.

   The mind and emotions are auxiliary to each other. Passion is auxiliary to art.

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noun

plural

auxiliaries

1. a person or thing that gives aid of any kind; helper.

   Synonyms:

   help, assistant, ally, aide

2. an organization allied with, but subsidiary to, a main body of restricted membership, especially one composed of members' relatives.

   The men's club and the ladies' auxiliary were merged into one organization.

3. auxiliary verb.

4. auxiliaries, foreign troops in the service of a nation at war.

5. Navy. a naval vessel designed for other than combat purposes, as a tug, supply ship, or transport.

6. Nautical. a sailing vessel carrying an auxiliary propulsion engine or engines.

auxiliary British  

/ -ˈzɪlə-, ɔːɡˈzɪljərɪ /

adjective

1. secondary or supplementary

2. supporting

3. nautical (of a sailing vessel) having an engine

   an auxiliary sloop

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noun

1. a person or thing that supports or supplements; subordinate or assistant

2. nautical

   1. a sailing vessel with an engine

   2. the engine of such a vessel

3. navy a vessel such as a tug, hospital ship, etc, not used for combat

Etymology

Origin of auxiliary

1595–1605; < Latin auxiliārius assisting, aiding, helping, equivalent to auxili ( um ) aid, help ( aux ( us ) increased, augmented (past participle of augēre: aug- increase + -sus, variant of -tus past participle suffix) + -ilium noun suffix) + -ārius -ary

Example Sentences

He added that France's partners would also share in the development of "auxiliary" capacities under the new nuclear doctrine: space-based alarm systems; air defence to shoot down incoming drones and missiles; and long-range missiles.

From BBC • Mar. 2, 2026

On Thursday, the company said "a leak of drilling fluid was identified in two auxiliary lines" connecting the drilling rig to a well about 175 kilometers offshore.

From Barron's • Jan. 6, 2026

On the island, Laczko waited as mechanics tried to fix the plane’s auxiliary power unit that sits in the tail of the plane.

From The Wall Street Journal • Dec. 22, 2025

Surgeons implanted an auxiliary liver graft derived from a genetically modified Diannan miniature pig featuring 10 targeted gene alterations.

From Science Daily • Dec. 7, 2025

Thanks to auxiliary fuel tanks and slender, ultraefficient Davis wings, it could fly literally all day, a decisive asset in the sprawling World War II theaters.

From "Unbroken" by Laura Hillenbrand

Related Words

• ancillary