Involute

A curve that cuts all tangents of another curve at right angles; traced by a point on a string that unwinds from a curved object.

To roll or curl inwards.

Difficult to understand; complicated.

Having the edges rolled with the adaxial side outward.

(of shells) Having a complex pattern of coils in which younger whorls only partly surround older ones.

Turned inward at the margin, like the exterior lip of the shells of species in genus Cypraea.