a piece of clothing that has no sleeves and that covers the top of half of the body, worn especially to show big arm muscles

Muscle vests are great for showing off your physique. 肌肉背心非常能够凸显你强健的体格。

He was wearing a muscle vest and one of his arms was covered in tattoos. 他穿着一件肌肉背心，一只手臂上布满了纹身。