crust

n.

1. 面包皮; 糕饼等的酥皮
   • The crust of the bread is burnt.
     这块面包的外皮烤焦了。
2. (泥土、雪等)硬的外层
   • The crust on the snow was thick enough for us to walk on it.
     冻结的雪面够厚, 我们可以在上面行走。