The Oxford Thesaurus An A-Z Dictionary of Synonyms - brain n.

1) brains, intelligence, intellect, understanding, sense, thought, imagination, capacity, perspicacity, perceptiveness, perception, percipience; wisdom, sagacity, wit, discernment, acumen; knowledge, cognition: Although she's not yet ten, she has the brain to become a great mathematician. 2) genius, mastermind, intellectual; leader, planner: Many people regard Einstein as the greatest brain of the 20th century. Ivor was clearly the brains of the operation.