A muffin top is if the girl shirt is up, and you can see her tummy going over the belt line.

游泳圈指的是如果把女孩的衬衫拉起来，你可以看到她的肚子越过皮带线。

He almost failed to see the needle point flick out beneath the belt line.

他差点没看到腰带下的针尖弹了出来。