ACCESSARY is a 9 letter word that starts with A.

1. \Ac*ces"sa*ry\ (#; 277), a.
   Accompanying, as a subordinate; additional; accessory; esp.,
   uniting in, or contributing to, a crime, but not as chief
   actor. See {Accessory}.
         To both their deaths thou shalt be accessary. --Shak.
         Amongst many secondary and accessary causes that
         support monarchy, these are not of least reckoning.
                                                  --Milton.
   

2. \Ac*ces"sa*ry\ (277), n.; pl. {Accessaries}. [Cf.
   {Accessory} and LL. accessarius.] (Law)
   One who, not being present, contributes as an assistant or
   instigator to the commission of an offense.
   {Accessary before the fact} (Law), one who commands or
      counsels an offense, not being present at its commission.
   {Accessary after the fact}, one who, after an offense,
      assists or shelters the offender, not being present at the
      commission of the offense.
   Note: This word, as used in law, is spelt accessory by
         Blackstone and many others; but in this sense is spelt
         accessary by Bouvier, Burrill, Burns, Whishaw, Dane,
         and the Penny Cyclopedia; while in other senses it is
         spelt accessory. In recent text-books on criminal law
         the distinction is not preserved, the spelling being
         either accessary or accessory.