conspirator
n. countable C1 Advanced US //kənˈspɪɹətɝ// UK //kənspˈɪɹətɐ// con·spir·a·tor
n. someone who secretly works with others to do something illegal or harmful. You use this word for people who plan a crime or a secret plot together.
n. a person who secretly agrees with others to commit an illegal or harmful act. Often implies a shared intent and a degree of premeditation.
The police arrested a conspirator in the bank robbery.
During the trial, the witness testified that he was a conspirator in the plot to overthrow the government.
Historians often debate whether the accused was a genuine conspirator or merely a pawn who was unaware of the full scale of the treasonous scheme.
From Anglo-Norman conspiratour.