The term BRAINY GROUP can be summarized by two crossword solutions: MENSA (5 letters) and THINKTANK (9 letters). MENSA is an international organization for people with high IQs, founded in England in 1946. It is a non-profit organization that provides a forum for intellectual exchange among its members. THINKTANK is a term used to describe a group of experts who come together to discuss and analyze a particular issue or problem. They are often used to provide advice and guidance to governments and other organizations.