adjective

1. giving help or aid; assisting or supporting
2. acting in a subsidiary, or subordinate, capacity
3. additional; supplementary; reserve
4. having an engine that can be used for supplementary power, as a sailing vessel
5. designating or of any of the noncombat ships, as tankers or tenders, that form the service fleet of a navy

Etymology: L auxiliaris, helpful < auxilium, aid < pp. of augere, to increase: see wax

noun pl. auxiliaries -·ries

1. an auxiliary person or thing
2. foreign or allied armed forces aiding those of a country at war
3. an assisting or supplementary group or organization this club has a women's auxiliary
4. an auxiliary vessel or ship
5. Gram. auxiliary verb