stuffed shirt

1. N-COUNT If you describe someone, especially someone with an important position, as a stuffed shirt, you mean that they are extremely formal and old-fashioned. (尤指身居要职的)一本正经的人; 古板守旧的人[非正式]

In a pinstriped suit he instantly looked like a stuffed shirt. 穿上一套细条纹西装后，他马上就显得一本正经。