exercise ball
noun🔊/ˈeksəsaɪz bɔːl/
🔊/ˈeksərsaɪz bɔːl/
(North American English also stability ball)
a large ball that you can sit on when doing exercises to make your muscles work in a different way 健身球 Sit upright on the exercise ball with your feet flat on the floor. 直立坐在健身球上，双脚平放在地板上。