If you said an egg is an oval, you're right!

The actual mathematical description is an oblate spheroid. 

The word spheroid means that the egg is like a sphere, but isn't exactly a sphere. That's because an egg isn't perfectly round. The word oblate means that the poles of the egg are flattened or depressed. 

So, an egg is a 'not-quite-round sphere' with flattened sides. You could also say that it's an oval with one end larger than the other. Either way they really are one of nature's perfect food containers.