A chignon is a sleek, elegant hairdo that's similar to a bun. A ballerina might pull her hair back into a chignon.
Many formal events, like weddings and proms, call for fancy hair styles — a classic one is the chignon. While a bun may be high on the head, a chignon is almost always coiled smoothly at the nape of the neck. In fact, the French word chignon literally means "nape of the neck," from the Old French chaignon, "iron collar or noose," which has a Latin root, catena, "chain or restraint."