We certainly can define life, it's just that people don't generally agree on a definition. Some people get offended if you don't include their favorite things in your definition.
Even so, we understand it just the same no matter how you define it, because what we understand is not a function of word choice or definition. It's a function of capability.
We can't really define life in the first place.
But this is not necessarily to your favour. I think it's more of an indication of how the world doesn't fit into our... anthropomorphic way of thinking. That is, everything follows the laws of physics, no magic involved. We aren't special.