A chapeau is a flat-topped
hat
A hat is a head covering which is worn for various reasons, including protection against weather conditions, ceremonial reasons such as university graduation, religious reasons, safety, or as a fashion accessory. Hats which incorporate mecha ...
once worn by senior clerics.
In heraldry
In European
ecclesiastical heraldry
Ecclesiastical heraldry refers to the use of heraldry within Christianity for dioceses, organisations and Christian clergy. Initially used to mark documents, ecclesiastical heraldry evolved as a system for identifying people and dioceses. It ...
, it is used as a mark of