Parabolic portion is a term used to describe the curved shape of an ARC. It is commonly used in mathematics and engineering to describe the shape of a parabola, which is a two-dimensional curve that is symmetrical about its vertex. An ARC is a part of a circle or other curved line, and a parabolic portion is a section of an ARC that follows the shape of a parabola. This term is often used in architecture and engineering to describe the shape of a structure or object.