Sheer folly is a term used to describe an act or decision that is extremely foolish and irrational. It is often used to describe a situation in which someone has acted without considering the consequences of their actions. The crossword solution for this term is 'IDIOCY, ' which is defined as a lack of good sense or judgment. This term is often used to describe someone who has made a foolish decision or acted in a way that is not rational.