The Collaborative International Dictionary of English v.0.48:

Ancillary \An"cil*la*ry\, a. [L. ancillaris, fr. ancilla a
   female servant.]
   Subservient or subordinate, like a handmaid; auxiliary.
   [1913 Webster]

         The Convocation of York seems to have been always
         considered as inferior, and even ancillary, to the
         greater province.                        --Hallam.
   [1913 Webster]

WordNet (r) 3.0 (2006):

ancillary
    adj 1: furnishing added support; "an ancillary pump"; "an
           adjuvant discipline to forms of mysticism"; "The mind and
           emotions are auxiliary to each other" [syn: accessory,
           adjunct, ancillary, adjuvant, appurtenant,
           auxiliary]