auxiliary (auxiliaries plural )
1 n-count An auxiliary is a person who is employed to assist other people in their work. Auxiliaries are often medical workers or members of the armed forces.
(=ancillary)
Nursing auxiliaries provide basic care, but are not qualified nurses.
2 adj Auxiliary staff and troops assist other staff and troops.
The government's first concern was to augment the army and auxiliary forces.
3 adj Auxiliary equipment is extra equipment that is available for use when necessary.
...an auxiliary motor.
4 n-count In grammar, an auxiliary or auxiliary verb is a verb which is used with a main verb, for example to form different tenses or to make the verb passive. In English, the basic auxiliary verbs are `be', `have', and `do'. Modal verbs such as `can' and `will' are also sometimes called auxiliaries.