aux·il·ia·ry 
(ôg-zĭlyə-rē, -zĭlə-rē)
(ôg-zĭlyə-rē, -zĭlə-rē)adj.
1. Giving assistance or support; helping.
2. Acting as a subsidiary; supplementary: the main library and its auxiliary branches.
3. Held in or used as a reserve: auxiliary troops; an auxiliary power generator.
4. Nautical Equipped with a motor as well as sails.
5. Grammar Of, relating to, or being an auxiliary verb.
n. pl. aux·il·ia·ries
1. An individual or group that assists or functions in a supporting capacity: a volunteers' auxiliary at a hospital.
2. A member of a foreign body of troops serving a country in war.
3. Grammar An auxiliary verb.
4. Nautical
a. A sailing vessel equipped with a motor.
b. A vessel, such as a supply ship or a tug, that is designed for and used in instances and services other than combat.
[Middle English, from Latin auxiliārius, from auxilium, help; see aug- in the Appendix of Indo-European roots.]