sheath            
noun [ C ] uk/ʃiːθ/ us/ʃiːθ/
 鞘套;护皮
a close-fitting covering to protect something
  The cable has a copper wire surrounded by a plastic sheath. 电缆是铜丝做的,外面包着塑料皮。 
 The nerves are protected by thin sheaths of fatty tissue. 神经由薄薄的脂肪鞘保护着。 
  (刀剑的)鞘
a cover into which a knife or sword fits so that the blade cannot cut someone when it is not being used
  He drew the knife from its jewelled leather sheath. 他把刀从镶有珠宝的皮鞘中抽出来。 
  UK避孕套(同 condom) 
a  condom