123 ways ...

Life, what is that? DNA??? What if life on other planets doesn't use DNA to replicate or can silicon life forms function, albeit possibly slower than carbon based, along the lines of life as we know it? This is a question researchers far more know legible that yours truly have been pondering about for years on end. 

To whit.

In 2011, Trifonov reviewed 123 definitions of life. Each was different, but the same words showed up again and again in many of them. Trifonov analyzed the linguistic structure of the definitions and sorted them into categories. Beneath their variations, Trifonov found an underlying core. He concluded that all the definitions agreed on one thing: life is self‐reproduction with variations. What NASA’s scientists had done in eleven words (“Life is a self‐sustained chemical system capable of undergoing Darwinian evolution”), Trifonov now did with three.

Seems Trifonov did away with the DNA part without issue but the quandary remains, what is life?

As analogy ...

These philosophers are following in the tradition of Ludwig Wittgenstein. In the 1940s, Wittgenstein argued that everyday conversations are rife with concepts that are very hard to define. How, for example, would you answer the question, “What are games?”

In the 1990s, some researchers suggested that the meteorite Allan Hills 84001 (up), a fragment of Mars that landed in Antarctica, contained fossils of ancient Martian microbial life (immediately above). Their argument was largely discounted by other scientists.

Seems the life definition conundrum will continue, doesn't it?