Darya was beginning to understand why she might be ruined forever for academic life. Certainly, the world of ideas had its own pleasures and thrills.… - Charles Sheffield

I’d make a case for saying anything that propagates itself in an intentional way qualifies to be thought of as alive.

Could it wipe out life on Earth?"
"Oh, I very much doubt that. Single-celled and oceanic forms will presumably survive. But it might make life impossible for humans."
"Actually, that tends to be my primary concern. Sponges and oysters will have to take care of themselves.

If I’ve learned one thing wandering around inside and outside the Solar System, it’s this: Nature has more ways of killing you than you can imagine. When you think you’ve learned them all, another one pops up to teach you humility—if you’re lucky. If not, someone else will have to decide what did you in.