- [countable, uncountable]
the hard outer part of eggs, nuts, some seeds, and some animals （蛋、坚果、某些种子和某些动物的）壳 
We collected shells on the beach. 我们在海滩拾贝壳。 snail/oyster/clam shells 蜗牛/牡蛎/蛤壳 walnut shells 核桃壳 earrings made out of coconut shell 用椰子壳做的耳坠 the shell of a turtle 乌龟的壳
Extra ExamplesTopics Fish and shellfishb1, Animalsb1Male crabs shed their shells twice a year. 公螃蟹每年蜕壳两次。 Remove the mussels from their shells. 把贻贝从壳中取出。 The snail went back into its shell. 蜗牛缩回壳里。 There was a hard outer shell and a tough inner shell. 有坚硬的外壳和坚韧的内壳。
Oxford Collocations Dictionaryadjective- empty
- hard
- outer
- …
- have
- come out of
- emerge from
- …
- [countable]
any object that looks like the shell of a snail or sea creature 壳状物 pasta shells 贝壳形意大利面
- [countable]
a metal case filled with explosive, to be fired from a large gun 炮弹 mortar/artillery shells 迫击炮/炮弹 A shell burst only yards away from us. 一颗炮弹在距离我们仅几码处爆炸。 Several empty shell casings were found in the area. 在该地区发现了几个空弹壳。
Extra ExamplesTopics War and conflictc2Two shells hit the roof. 两颗炮弹击中了房顶。 They braved heavy shell fire to rescue the wounded. 他们冒着猛烈的炮火去抢救伤员。 The telltale sound of an incoming shell was heard. 能清晰地听到炮弹正呼啸而来。 a heap of spent brass shells from a machine gun 一堆废旧的机关枪铜弹壳
Oxford Collocations Dictionaryadjective- unexploded
- spent
- anti-aircraft
- …
- load
- fire
- fly
- fall
- land
- …
- fire
- shock
- case
- …
- (North American English) (also cartridge British and North American English)[countable]
a tube or case containing explosive and a bullet or shot, for shooting from a gun 炮弹 - [countable]
the walls or outer structure of something, for example, an empty building or ship after a fire or a bomb attack （房屋或船舶等的）骨架，框架，壳体 The house was now a shell gutted by flames. 房子烧得只剩个空骨架了。 - (figurative)
My life has been an empty shell since he died. 他死后，我的生活就成了一个徒有其表的空壳子。 The fire reduced the school to a hollow shell. 学校烧得只剩个空骨架了。
Oxford Collocations Dictionaryadjective- concrete
- burned-out
- empty
- …
- [countable]
any structure that forms a hard outer frame （任何物体的）外壳，壳体 the body shell of a car 车身外壳
- [singular]
the outer layer of somebody’s personality; how they seem to be or feel （人的）表面性格，表面人格，表面感情，外表 She had developed a shell of indifference. 她养成一副冷漠的外表。 She had built up a protective shell around herself. 她给自己建了个“保护壳”，躲了进去。
Word OriginOld English scell (noun), of Germanic origin; related to Dutch schel ‘scale, shell’, also to scale ‘thin plates that cover the skin of many fish and reptiles’. The verb dates from the mid 16th cent. in sense (2).
Idioms
come out of your shell
to become less shy and more confident when talking to other people （和人交谈时）放大胆子，不缩手缩脚 He’s really come out of his shell since he met Marie. 自遇到玛丽以后，他真的变开朗了。
to go, retreat, etc. into your shell
to become shyer and avoid talking to other people 变得羞怯（或内向、孤僻） Whenever my friends are here, she just withdraws into her shell. 每当我的朋友在这里时，她就退缩到她的壳里。