a charley horse, a sudden, painful tightening of a muscle in your arm or leg，美语里非正式用语，意思就是我们常遇到的“抽筋”、“很突然的肌肉僵疼”，类似cramp或kink；例如：I got a charley horse in my leg and had to stop running. 我突然腿抽筋起来，只好停止跑步