A market-wide trading halt refers to the temporary suspension of trading across all securities or a significant portion of the stock market. It's typically implemented when there's a severe disruption or crisis that impacts the functioning of the market.

For example, if there's a sharp decline in the overall market, as measured by an index such as the S&P 500, circuit breakers may be triggered, leading to a temporary halt in trading. Circuit breakers are designed to automatically pause trading to allow investors to reassess and prevent panic selling.

During a market-wide trading halt, investors are unable to buy or sell securities until the halt is lifted. The duration of a market-wide trading halt can vary.