A sailing term referring to the directions in which a boat cannot point and still maintain good airflow over its sail. For a sail to work properly it must be pointing at an angle to the wind, and if the boat is pointing at too small an angle to the wind the sail cannot work efficiently. As the angle of the boat to the wind gets smaller the sail works less and less well until a point where airflow is completely detached. A boat can usually point at around 45 degrees to the wind and maintain perfect airflow leading to the 90 degree segment around the wind direction being called the “no-go zone.”

A boat stuck in the no-go zone with its sail not working and with very little speed is said to be “in irons.” The no-go zone is also referred to as the wind-widow in power kiting.