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.

---

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

---

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

But the celebrations in one Tehran neighborhood were also furtive and short lived to avoid riot police or members of the Basij, a voluntary auxiliary force with the Revolutionary Guards.

From Los Angeles Times • Mar. 1, 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

According to the Geneva Conventions, to which Russia is a party, former POWs can’t be employed on active military service, only in auxiliary roles.

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

Entire classes of high school boys were drafted into the antiaircraft auxiliary.

From "Hitler Youth: Growing Up in Hitler's Shadow" by Susan Campbell Bartoletti

Related Words

• ancillary