Being coiled, curled, or rolled in at the edge.

1. A curve produced by any point of a perfectly flexible inextensible thread that is kept taut as it is wound upon or unwound from another curve.

2. A curve that lies on the tangent surface of a given space curve and is orthogonal to the tangents to the given curve.

3. A surface for which a given surface is one of the two surfaces of center.