A stop-out occurs when your margin level falls to a specific percentage level (at Amega, the percentage is 20%), causing one or all of your trading positions to be closed automatically.
The reason for this is that your trading account has reached a margin so low that it can no longer sustain the open positions.
It is the equivalent of a Game Over message on a video game.
A stop-out can be prevented as far as the Margin Call point. After that, it is impossible to stop, so it is a good practice to keep a close eye on your trades, especially when they are at a loss.
Risk management tools such as stop-loss and take-profit are critical in preventing a stop-out. Always have at least one in place, before opening a position.