For the record: I’m not the one changing the meaning of the word. I use it like in the definition. You’re the one extending the meaning arbitrarily.
I think I’ll just wait and see if some expert comes along and gives me my single example. If that doesn’t happen I’m going to stick to my opinion: They exist in theory, but not in practice. And vulnerabilities and rootkits exist, but a vulnerability isn’t automatically called a virus because those are different things.
To end with some more friendly words: I’m pretty sure some people are confusing the words ‘malware’ and ‘virus’. Malware is the umbrella term. I’ve already admitted there is malware. For example the Mirai worm i think had affected hundreds of thousands of IoT devices (speaking of fire and forget embedded linux). And I’ve seen wordpress plugins with vulnerabilities and actual rootkits on webservers myself, as I told earlier. But I’ve also said in this context the distinction matters.