His addle-brained idea of putting salt in coffee made everyone sigh in disbelief.

addle-brained 是由形容词 addle（糊涂的、混乱的）和名词 brain（头脑）组成的复合形容词，中间用连字符连接。addle 原指"变质的（蛋）"，引申为"糊涂的"；brain 指"大脑、头脑"。 addle-brained 字面意思是"头脑像坏掉的蛋一样糊涂的"，形容"思维混乱、愚蠢糊涂的"。