The Collaborative International Dictionary of English v.0.48:

Accomplice \Ac*com"plice\, n. [Ac- (perh. for the article a or
   for L. ad) + E. complice. See Complice.]
   [1913 Webster]
   1. A cooperator. [R.]
      [1913 Webster]

            Success unto our valiant general,
            And happiness to his accomplices!     --Shak.
      [1913 Webster]

   2. (Law) An associate in the commission of a crime; a
      participator in an offense, whether a principal or an
      accessory. "And thou, the cursed accomplice of his
      treason." --Johnson.

   Note: It is followed by with or of before a person and by in
         (or sometimes of) before the crime; as, A was an
         accomplice with B in the murder of C. Dryden uses it
         with to before a thing. "Suspected for accomplice to
         the fire." --Dryden.
         [1913 Webster]

   Syn: Abettor; accessory; assistant; associate; confederate;
        coadjutor; ally; promoter. See Abettor.
        [1913 Webster]

The Devil's Dictionary (1881-1906):

ACCOMPLICE, n.  One associated with another in a crime, having guilty
knowledge and complicity, as an attorney who defends a criminal,
knowing him guilty.  This view of the attorney's position in the
matter has not hitherto commanded the assent of attorneys, no one
having offered them a fee for assenting.


Moby Thesaurus II by Grady Ward, 1.0:

27 Moby Thesaurus words for "accomplice":
   a party to, abettor, accessary, accessory, accomplice in crime,
   ally, assistant, associate, coconspirator, cohort, collaborator,
   colleague, confederate, conspirator, copartner, cotenant, fellow,
   fellow conspirator, henchman, partaker, participant, participator,
   partner, party, shareholder, sharer, socius criminis