conspirator

noun

1. One of a group that acts in harmony to do something unlawful and unethical; a person who is part of a conspiracy.

   “The conspirators were rounded up by the police and arrested.”

   “All the Jacobite gentry of that part of the country were collected together; though, it must be confessed, their appearance and their usual after-dinner conversation were rather at variance. Now they looked calm and comfortable, with as little the appearance of conspirators as possible; then they were (by their own account) the most oppressed of individuals, and the most devoted of partisans, ready to die, so that their wrongs were redressed, and the rightful king restored.”