auxiliary

adj

1. (not-comparable)Helping; giving assistance or support.

   “auxiliary troops”

2. (not-comparable)Supplementary or subsidiary.
3. (not-comparable)Held in reserve for exceptional circumstances.
4. (not-comparable)Of a ship, having both sails and an engine.
5. (not-comparable)Relating to an auxiliary verb.

noun

1. A person or group that acts in an auxiliary manner.

   “Auxiliaries and ancillaries are comprehensive, and include a Westinghouse motor-driven recriprocating compressor used for locomotive braking and general service air, two rotary exhauster sets for train brakes when hauling passenger or fitted freight trains, and an oil-fired train heating boiler.”

   “A drive to exploit the Highlands as a winter sports area, with all the necessary auxiliaries, such as chair lifts in the Cairngorms, shows increasing promise, […].”

   “Summer “felt betrayed” that a close friend had used AI as “an auxiliary” to talk to her.”

2. A sailing vessel equipped with an engine.
3. (abbreviation, alt-of, ellipsis)Ellipsis of auxiliary verb.

   “The three traditionally recognized Non-modal Auxiliaries are the per- fective Auxiliary have, the progressive Auxiliary be, and the passive Auxiliary be. Perfective have is so-called because it marks the completion (hence, perfec- tion) of an action; it is followed by a VP headed by a perfective -n participle, as in: (121) The referee has [_(VP) shown him the red card]”

4. A marching band color guard.