conspirer
/kɑnˈspɪrər/Definitions
1. noun
A person who joins or is involved in a conspiracy, especially one who secretly plans or plots with others.
“The government suspected several conspirers in the plot to overthrow the regime.”
2. verb
To secretly plan or plot with others, especially to achieve a goal or carry out an action.
“The group began to conspire against their corrupt leader.”