ancillary UK /ænˈsɪl.ə.ɹiː/US /ˈæn.səˌlɛɹ.i/noun 2adjective 1forms 3 noun2 •Something that serves an ancillary function, such as an easel for a painter. •An auxiliary. adjective1 •Subordinate; secondary; auxiliary.[…] how easily he took all things along with him,—the persons, the opinions, and the day, and nature became ancillary to a man. — 1836 formsancillaries · more ancillary · most ancillary