WordNet (r) 3.0 (2006):

mastermind
    n 1: someone who creates new things [syn: originator,
         conceiver, mastermind]
    2: someone who has exceptional intellectual ability and
       originality; "Mozart was a child genius"; "he's smart but
       he's no Einstein" [syn: genius, mastermind, brain,
       brainiac, Einstein]
    v 1: plan and direct (a complex undertaking); "he masterminded
         the robbery" [syn: mastermind, engineer, direct,
         organize, organise, orchestrate]

Moby Thesaurus II by Grady Ward, 1.0:

121 Moby Thesaurus words for "mastermind":
   academician, ace, architect, authority, be responsible for,
   bookman, brains, call the signals, captain, carry on, classicist,
   clerk, colossus of knowledge, command, conceive, conceiver,
   conduct, contriver, control, crackerjack, create, creator, design,
   develop, devise, direct, doctor, elder, elder statesman, engineer,
   first-rater, generate, genius, giant of learning, good hand,
   govern, great, great soul, guru, handle, head, head up, humanist,
   illuminate, intellect, intellectual, lead, lead on, learned clerk,
   learned man, literary man, litterateur, lover of learning,
   lover of wisdom, magician, mahatma, make the rules, man of genius,
   man of intellect, man of learning, man of letters, man of wisdom,
   manage, mandarin, maneuver, manipulate, master, master hand,
   mentor, mind, mine of information, officer, oracle, order,
   organize, past master, philologist, philologue, philomath,
   philosophe, philosopher, plan, planner, polyhistor, polymath,
   practiced hand, prescribe, prodigy, pull the strings, pundit,
   quarterback, rabbi, regulate, rishi, run, sage, sapient, savant,
   scholar, scholastic, schoolman, seer, skilled hand, skipper, star,
   starets, student, superstar, take command, take the lead, think up,
   thinker, topnotcher, virtuoso, walking encyclopedia, whiz,
   wise man, wise old man, wizard, work out, work up