Both "oval" and "oblong" are adjectives often used to describe shapes or outlines. While "oval" is defined as "having the general form, shape, or outline of an egg," "oblong" is defined as "elongated, usually from the square or circular form."
An oval can be classified as an oblong or elongated circle. An object with an oval shape can be described as oblong, but not all oblong objects can be described as oval. Other words used to describe oval shapes are elliptical and ellipsoidal.
Oblong objects can be elongated circles, such as ovals, but can also be elongated squares. A second definition of oblong is "in the form of a rectangle one of whose dimensions is greater than the other."