In all the instances I've been able to think of off the top of my head: how the egg is named depends on whether it's in a culinary/food-centric context.

When you're referring to an egg in its natural state, the egg is named for the animal that produced it, like duck egg, goose egg, etc.

When referring to an egg that has been prepared, or something that is not an actual egg from an animal, you'd refer to it based on the preparation or what the fake egg is made of, like fried egg, boiled egg, faberge egg, or chocolate egg.

I would posit that the question can't truly be answered in its current form; the question is assumed to be asking about a unaltered egg produced by a chicken, but does not explicitly state whether the egg was transformed in some way, and does not state that the egg being referred to is specifically from a chicken.

Yes I'm fun at parties and no I will not be taking questions at this time :)

Edit: Formatting

but then if a turtle crawls out of that egg it ceases being a chicken egg and becomes

I don't think I support this definition. It's too loose. You can't have it both ways. It is what it is when it is formed. It doesn't change after it has been laid. It's genetically primed from the DNA of its parents. Not from what's going on inside the egg.

Either way, I personally don't subscribe to the whole "chicken egg" definition issue at all. An egg is just the shell. The important part is what's inside it. And either way, both definitions can be easily answered by evolution, so it's never a difficult question.

If the definition is of importance, just ask for that info, then answer accordingly. No big deal. 👍