circuit breaker n. a rule or law that puts protective measures in place once a certain level of financial activity has been reached; (specifically) a law that provides tax refunds once a maximum of property taxes have been paid; a rule that shuts down or limits trading action when a stock market’s value or activity changes more than a certain percentage. Editorial Note: In Australia and New Zealand an additional meaning of the term is used, given by the Macquarie Dictionary as “an event, activity, etc., which acts as a distraction from previous preoccupations and tensions.” (source: Double-Tongued Dictionary)