I. mas ‧ ter ‧ mind 1 /ˈmɑːstəmaɪnd $ ˈmæstər-/ BrE AmE noun [singular]
someone who plans and organizes a complicated operation, especially a criminal operation:
a criminal mastermind
mastermind of/behind
He is suspected of being the mastermind behind the bombings.
II. mastermind 2 BrE AmE verb [transitive]
to think of, plan, and organize a large, important, and difficult operation:
The project was masterminded by Morris, then aged 29.
Ridley, as commerce secretary, masterminded the privatisation.