1. One who conspires; one who engages in a plot to commit a crime, particularly treason.
2. In law, one who agrees with another falsely and maliciously to indict an innocent person of felony. By the British statute, a conspirator is defined to be one who binds himself by oath, covenant, or other alliance, to assist another falsely and maliciously to indict a person, or falsely to maintain pleas.