Source : Webster's Revised Unabridged Dictionary (1913)

Subsidiary \Sub*sid"i*a*ry\, a. [L. subsidiarius: cf. F.
   subsidiaire. See {Subsidy}.]
   1. Furnishing aid; assisting; auxiliary; helping; tributary;
      especially, aiding in an inferior position or capacity;
      as, a subsidiary stream.

            Chief ruler and principal head everywhere, not
            suffragant and subsidiary.            --Florio.

            They constituted a useful subsidiary testimony of
            another state of existence.           --Coleridge.

   2. Of or pertaining to a subsidy; constituting a subsidy;
      being a part of, or of the nature of, a subsidy; as,
      subsidiary payments to an ally.

            George the Second relied on his subsidiary treaties.
                                                  --Ld. Mahon.

Subsidiary \Sub*sid"i*a*ry\, n.; pl. {Subsidiaries}.
   One who, or that which, contributes aid or additional
   supplies; an assistant; an auxiliary. --Hammond.

Source : WordNet®

subsidiary
     adj 1: 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" [syn: {accessory}, {adjunct}, {ancillary},
             {adjuvant}, {appurtenant}, {auxiliary}]
     2: functioning in a subsidiary or supporting capacity; "the
        main library and its auxiliary branches" [syn: {auxiliary},
         {supplemental}, {supplementary}]

subsidiary
     n 1: an assistant subject to the authority or control of another
          [syn: {subordinate}, {underling}, {foot soldier}]
     2: a company that is completely controlled by another company
        [syn: {subsidiary company}]