an intelligent person who plans and directs a complicated project or activity (often one that involves a crime) （极具才智的）决策者；主谋；出谋划策者 The mastermind behind the robbery was never caught. 策划这宗抢劫案的幕后主脑始终没有抓到。 There’s a criminal mastermind behind all this. 所有这一切背后有一个主谋。