circuit breaker

1. General: Protective electrical switch that turns itself off (trips) to interrupt flow of electricity, if the current exceeds a preset limit. When the current returns to normal, the circuit breaker is either manually or automatically reset for reuse.

2. Program trading: Measure employed by modern commodity and stock exchanges (which use computerized trading systems) to temporarily halt automated trading when certain conditions (such as a precipitous fall in market prices) occur. Instituted after the third of Black Mondays (October 27, 1997), their objective is to prevent a 'melt down' (free-fall) of the market prices.