What "barn door" means in rock climbing

In rock climbing, the term "barn door" refers to a situation where one's body weight is not evenly distributed, causing the body to swing out like a barn door. This can occur when a climber's hands and feet are secure on only one side, causing their center of gravity to swing out from an overhang. It is an undesired effect that can cause a climber to lose balance, fall, or strain their arms.