sequin

sequin
/ˈsi:kwɪn; `sikwɪn/ n
small circular shiny disc sewn onto clothing as an ornament （衣物上作装饰用的）圆形小光片
    Her dress was covered in sequins which twinkled as she moved. 她的连衣裙上镶著小光片, 身体一动就闪闪发光.

牛津英汉双解词典