A strong litmus test as the one given by Andrei (creator of D for those not paying attention), settles the definition well enough. I'll even back off that claim because some absolutely refuse to accept a litmus test to meet definitions of things, as they're so hellbent on not being excluded. Unfortunately that's how language and the world works, not everyone gets their way.

So we'll just settle on once there's a commercially successful operating system built in a GC'd language then I'll eat crow but till then they're all going to be C/C++/D/Rust or built on similar abstraction layers. Go ahead, wash away Linux, iOS and Windows in the competitive landscape with something written in Go. Let's see it, that's believing after all. It'll never happen because it's unsuited and inferior for that purpose.