名詞 crust:

1. the outer layer of the Earth
   同義詞：Earth's crust
2. a hard outer layer that covers something
   同義詞：incrustation, encrustation
3. the trait of being rude and impertinent; inclined to take liberties
   同義詞：gall, impertinence, impudence, insolence, cheekiness, freshness

動詞 crust:

1. form a crust or form into a crust

1. The earth's crust is layered..
   地球的外殼是分層的。
2. The crust on the snow was thick enough for us to walk on it.
   外層的雪已經(jīng)凍硬，可以在上面行走。
3. The snow crusted the lake last night.
   昨夜的雪使湖面結了冰。

crust

n.（名詞）

The hard outer portion or surface area of bread.
面包皮：面包的表面區(qū)域的硬皮
A piece of bread consisting mostly of the hard outer portion.
硬面包片：主要由外表硬皮構成的面包片
A piece of bread that has become hard and dry.
干面包片：變硬變干的面包片
A pastry shell, as of a pie or tart.
餡餅皮：餡餅或果餡餅等的面團的外殼
A hard, crisp covering or surface:
堅硬表面：硬的、脆的外皮或外殼：
例句：
snow with a firm crust.
有一層堅硬冰面的雪

A hard deposit formed on the interior of a wine bottle as the wine matures.
酒垢：酒釀熟后在酒瓶內部生成的硬的沉積物
Geology
【地質學】
The exterior portion of the earth that lies above the Mohoroviôiô discontinuity.
地殼：位于莫霍洛維奇契不連續(xù)面之上的地球外層
The outermost solid layer of a planet or moon.
外殼：行星或月亮最外面的固態(tài)層
The hard outer covering or integument of certain plants and animals, such as lichens and crustaceans.
甲殼：某些植物或動物的硬的外層覆蓋物或包裹物，如地衣和甲殼綱動物
Pathology An outer layer or coating formed by the drying of a bodily exudate such as pus or blood; a scab.
【病理學】 痂：由身體的滲出液如濃液或血液等變干而形成的一層外皮或覆蓋物；痂
Informal Insolence; audacity; gall.
【非正式用語】 無禮；放肆；厚顏無恥
v.（動詞）
crust.ed,crust.ing,crusts
v.tr.（及物動詞）
To cover with a crust.
用硬皮覆蓋
To form into a crust.
在…上結硬皮
v.intr.（不及物動詞）
To become covered with a crust.
有外殼，有硬皮：變得覆有外殼，硬皮
To harden into a crust.
結硬皮：變硬結成硬皮

來源：
Middle English cruste
中古英語 cruste
from Old French crouste
源自 古法語 crouste
from Latin crusta * see kreus-
源自 拉丁語 crusta *參見 kreus-

【引伸】
crust.less
adj.（形容詞）