A hairstyle element where long sidelocks are tied back to join a (possibly unseen) hairbun or ponytail at the back of the head. If pulled straight back and taut they don't qualify as being sidelocks, so some amount of slack is required, such that they drape in a U-shape on either side of the head.
Possibly only one sidelock may be tied back, if so also tag asymmetrical hair.
Examples: