duffer

例句：

1. 1.He was always a duffer at maths.
   他数学一直很差。
2. 2.She's a real duffer at making decisions.
   她做决定总是很糟糕。
3. 3.The duffer had no idea what he was talking about.
   那个笨蛋根本不懂他在说什么。