His thickheaded insistence on his wrong decision annoyed everyone.

thickheaded 是由形容词 thick（厚的、浓密的）和名词 head（头）组成的复合形容词，字面意思是"头很厚"，比喻"头脑迟钝、顽固不化"。 在句中形容某人固执己见、不愿改变想法的状态。