1. Something joined or added to another thing, but not essentially a part of it. Learning is but an adjunct to our self. (Shak)
5. A key or scale closely related to another as principal; a relative or attendant key. See Attendant keys, under Attendant, a. Relating to something that is added but is not essential; an ancillary pump; an adjuvant discipline to forms of mysticism; The mind and emotions are auxilliary to each other.