Tabard n. : A sort of tunic or mantle formerly worn for protection from the weather. When worn over the armor it was commonly emblazoned with the arms of the wearer, and from this the name was given to the garment adopted for heralds.

Example:


Taxonomy
tabard, sleeves, free encyclopedia, front and back, officers of arms, coat of arms, outer garment, arms, the Earl, Herald, Middle Ages, British Heraldry, search, short coat, sleeveless, shoulder, men's clothing, clothing in the Middle Ages.

Defination from the web:
tabard is a short coat, either sleeveless, or with short sleeves or shoulder pieces, which was a common item of men's clothing in the Middle Ages, usually for outdoors. ... Peter O'Donoghue in his tabard at the Garter Service ...