There is no specific name.
There cannot be a shape with one straight side. And , if it is not straight, there are many many options available: a circle or ellipse being two of the better "behaved" shapes. A squiggly curve would do as well.
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A shape's sides are called faces.
A cylinder seems to fit the description
a circle
A seven sided shape is called a heptagon or a septagon.......
It's called a side or edge.