A chignon is hair that has been pulled back and tied or rolled into a smooth knot, usually at the back of the head or low on the neck. It is a neat, dressed-up style — the kind you see at a wedding, in ballet, or in an old portrait — not a loose, messy bun. People now say bun for almost any knot of hair; chignon is the more careful word, and it still feels a little French. It is used mainly of a woman’s hair. Though actually, the knot itself is just a way of putting hair up; the special idea is that it is smooth and done on purpose.