noun – A highly intelligent person; especially, one who plans and directs a project (American Heritage Dictionary). A person who originates or is primarily responsible for the execution of a particular idea, project, or the like (Dictionary.com).
Example; Steve Jobs was the mastermind behind Pixar.
transitive verb – To direct, plan or supervise, as in a project or activity (American Heritage Dictionary). To plan and direct (a usually complex project or activity), especially skillfully (Dictionary.com)
Example; Jesse James masterminded several successful bank robberies.