adjective aux·il·ia·ry \g-ˈzil-yə-rē, -ˈzil-rē, -ˈzi-lə-\

: available to provide extra help, power, etc., when it is needed

Full Definition of AUXILIARY

a :  offering or providing help
b :  functioning in a subsidiary capacity <an auxiliary branch of the state university>
of a verb :  accompanying another verb and typically expressing person, number, mood, or tense
a :  supplementary
b :  constituting a reserve <an auxiliary power plant>
:  equipped with sails and a supplementary inboard engine <an auxiliary sloop>

Examples of AUXILIARY

  1. a sailboat with an auxiliary engine
  2. <the auditorium has an auxiliary cooling system used only on particularly sweltering days>
  3. Travelers have also been griping about a lack of air-conditioning while planes are on the tarmac—even after delays stretch for hours. Airlines blame the problem on a breakdown of a plane's auxiliary power unit. —Darren Everson, Wall Street Journal, 8 Aug. 2007


Latin auxiliaris, from auxilium help; akin to Latin augēre to increase — more at eke
First Known Use: 15th century


noun aux·il·ia·ry \g-ˈzil-yə-rē, -ˈzil-rē, -ˈzi-lə-\

: a group that provides help or assistance

plural aux·il·ia·ries

Full Definition of AUXILIARY

a :  an auxiliary person, group, or device (see 1auxiliary); specifically :  a member of a foreign force serving a nation at war
b :  a Roman Catholic titular bishop assisting a diocesan bishop and not having the right of succession —called also auxiliary bishop
:  a sailing boat or ship equipped with a supplementary inboard engine
:  an auxiliary verb

Examples of AUXILIARY

  1. In 1944 Forrestal also began a program of sending black enlisted men to serve in a limited number of fleet auxiliaries. These were still not warships, but they were seagoing vessels and closer to the fighting Navy than the small harbor-defense craft and harbor auxiliaries that had initially been open to black crews. —The Golden Thirteen, 1993


(see 1auxiliary)
First Known Use: 1567
May 27, 2015
riot act Hear it
a vigorous reprimand or warning
Take a 3-minute break and test your skills!
How to use a word that (literally) drives some people nuts.
Test your vocab with our fun, fast game
Ailurophobia, and 9 other unusual fears