tough nut

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释义
狠角色；硬骨头
A situation, person, group, etc. which is difficult to deal with.

例句
Elaine :Whoo, she's a tough nut.My favorite kind.Except for cashews.(2 Broke Girls)
易雷恩：嚯，她够硬的，我最喜欢的类型。但腰果除外。（破产姐妹）