In geometry, an oval or ovoid is any curve resembling an egg or an ellipse, but not an ellipse. Unlike other curves, the term 'oval' is not well-defined and many distinct curves are commonly called ovals. These curves have in common that:

they are differentiable (smooth-looking), simple (not self-intersecting), convex, closed, plane curves;
their shape does not depart much from that of an ellipse, and
there is at least one axis of symmetry.