Open outcry is a method of trading used at stock and commodity exchanges that involves calling out the specific details of a buy or sell order, so that the information is available to all traders. The information is then usually written on boards so all traders can see it.
Open outcry trading requires exciting trading floors with brokers rushing around trying to get their orders on the board. Brokers tend to enjoy open outcry markets, particularly during the euphoria of bull markets.
Open outcry has largely been replaced by automated trading systems. These are cheaper, globally accessible, disseminate information perfectly and match orders perfectly.
There is evidence that open outcry trading floors can make for good dissemination of information in other ways. Traders can use cues such as noise levels and the behaviour of other traders to monitor where the important movements in the market are happening.