The Collaborative International Dictionary of English v.0.48:

Auxiliary \Aux*il"ia*ry\ (?; 106), a. [L. auxiliarius, fr.
   auxilium help, aid, fr. augere to increase.]
   Conferring aid or help; helping; aiding; assisting;
   subsidiary; as auxiliary troops.
   [1913 Webster]

   Auxiliary scales (Mus.), the scales of relative or
      attendant keys. See under Attendant, a.

   Auxiliary verbs (Gram.). See Auxiliary, n., 3.
      [1913 Webster]