1 helping, assisting, supportive, aiding, abetting; helpful, accessory, supplementary:
In a well-balanced mind, imagination and understanding are auxiliary to each other.
2 subordinate, additional, subsidiary, secondary, ancillary, extra, reserve; accessory:
Larger sailing vessels have an auxiliary motor in case the wind fails.
3 help, assistance, aid, support, accessory:
Knowing another language is a useful auxiliary in the study of your own.
4 helper, assistant, aide, alter ego, supporter, Colloq man Friday, girl Friday:
Let me introduce Pat, my auxiliary, who will help you if I am not available.