adj. & n.
adj. 1 (of a person, activity, or service) providing essential support to a central service or industry, esp. the medical service. 2 (often foll. by to) subordinate, subservient.
n. (pl. -ies) 1 an ancillary worker. 2 something which is ancillary; an auxiliary or accessory.
[ L ancillaris f. ancilla maidservant ]