What does "knock out" mean here?
Getting the wind "knocked out" of you means to hit your back or stomach forcefully that it feels as though you can't breathe. When you get hit in the stomach or back, your diaphragm starts to spasm, making it feel as though you cannot breathe. This gives the feeling as though the wind got "knocked out" of your lungs. Ex: She got the wind knocked out of her when the soccer ball hit her stomach. Ex: He fell on his back and got the wind knocked out of him.