Ceremonial dress

Costume having a primarily ritual or ceremonial purpose

Ceremonial dress is clothing worn for very special occasions, such as coronations, graduations, parades, religious rites, trials and other important events. In the western dress code hierarchy of dress codes, ceremonial dress is often considered one of the most formal, in other cultures ceremonial dresses vary widely having entirely different meanings, and styles.

This keyword could refer to multiple things. Here are some suggestions: