What does "accomplice" mean?

Accomplice: (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. See Abettor.