Wearing ill-fitting clothes to the interview made him feel undignified.

undignified 是由前缀 un-（表示否定）和形容词 dignified（有尊严的）组成的形容词。dignified 来自名词 dignity（尊严），加上后缀 -ed 变成形容词，表示"有尊严的"。所以 undignified 意思是"没有尊严的、丢脸的"。