A halt in trading is a temporary stop in the trading of a security. If a common stock is halted, all derivatives and convertibles will be halted as well.
Applying "Halt in trading" to Securities Exams:
A halt in trading may occur if there is significant news pending, a sudden influx of orders or if the stock price has moved significantly and has triggered the single stock circuit breaker. If the trading in a stock is halted as a result of news pending the market place will be able to digest the information and price the security accordingly as a result of the news. Trading halts may last a few minutes or in extreme cases a few days.