A circle is defined as a round planar figure. All points on the circumference of a circle are equidistant from the center point. A circle is a one-dimensional figure.
Note that a sphere is the 3D model of a circle. So, any spherical shape can be represented in 1D as a circle
So, any shape that fits the above description can be modeled as circle.
Examples are:
a coin, the full moon, a clock, the sun, a tire, a round plate, a complete pizza,...etc