auxiliary
Americanadjective
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additional; supplementary; reserve.
an auxiliary police force.
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used as a substitute or reserve in case of need.
The hospital has an auxiliary power system in case of a blackout.
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(of a boat) having an engine that can be used to supplement the sails.
an auxiliary yawl.
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giving support; serving as an aid; helpful.
The mind and emotions are auxiliary to each other. Passion is auxiliary to art.
noun
plural
auxiliaries-
a person or thing that gives aid of any kind; helper.
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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.
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auxiliaries, foreign troops in the service of a nation at war.
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Navy. a naval vessel designed for other than combat purposes, as a tug, supply ship, or transport.
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Nautical. a sailing vessel carrying an auxiliary propulsion engine or engines.
adjective
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secondary or supplementary
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supporting
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nautical (of a sailing vessel) having an engine
an auxiliary sloop
noun
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a person or thing that supports or supplements; subordinate or assistant
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nautical
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a sailing vessel with an engine
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the engine of such a vessel
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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
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
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
A recent study in the Journal of Hepatology describes the first successful auxiliary liver xenotransplant from a genetically engineered pig into a living human.
From Science Daily • Dec. 7, 2025
Although auxiliary deputy sheriffs are volunteer positions, they can have law-enforcement powers equivalent to those of paid officers.
From BBC • May 27, 2025
Armies combined together in such a fashion are much better than a purely auxiliary force or a purely mercenary army, but are greatly inferior to one’s own troops.
From "The Prince" by Niccolò Machiavelli
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
