1. [n]  someone who acts as assistant
2. [adj]  functioning in a subsidiary or supporting capacity; "the main library and its auxiliary branches"
3. [adj]  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"

AUXILIARY is a 9 letter word that starts with A.

1. \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.
   {Auxiliary scales} (Mus.), the scales of relative or
      attendant keys. See under {Attendant}, a.
   {Auxiliary verbs} (Gram.). See {Auxiliary}, n., 3.
   

2. \Aux*il"ia*ry\, n.; pl. {Auxiliaries}.
   1. A helper; an assistant; a confederate in some action or
      enterprise.
   2. (Mil.) pl. Foreign troops in the service of a nation at
      war; (rarely in sing.), a member of the allied or
      subsidiary force.
   3. (Gram.) A verb which helps to form the voices, modes, and
      tenses of other verbs; -- called, also, an auxiliary verb;
      as, have, be, may, can, do, must, shall, and will, in
      English; [^e]tre and avoir, in French; avere and essere,
      in Italian; estar and haber, in Spanish.
   4. (Math.) A quantity introduced for the purpose of
      simplifying or facilitating some operation, as in
      equations or trigonometrical formul[ae]. --Math. Dict.