Originally Posted by Zephyr11

Meh, I've seen some really skilled cx guys on some of my mountain bike rides. Heil Valley Ranch into Picture Rock in Boulder, for example, is non-technical enough that I've seen cx guys on it, but it's a far cry from a road ride.

There's no clean line. You could try to separate it using the surface you're riding on, but then I'll give you the example of a guy on a road bike on a fire road versus a guy on a mountain bike riding urban assault. Don't worry about trying to label it, just do what you enjoy and don't overthink it.