One could take the definition of an enduro bike based on the size of the stroke, the size of the wheels and a few other sizes, juggling the terms "trail", "all-mountain", "OverMountain" and a few more, which even the manufacturers themselves no longer cover. Let's make a deal: an enduro bike is one that you can ride all day with your friends in the mountains. Up, down, sideways and as soon as you think of it.
You can pull up various elements under the enduro, but some things are the same: mountains, bikes, looking for new great paths to ride, and then some racing with your friends. Is it different from the beginning of MTB, when Gary Fisher, Joe Breeze and the rest of the Californian team organized their first Repack races some 50 years ago? Answer yourself within your own definition of enduro!