Again this depends on your definition of life, which is why I hate dictionaries being thrown around. If you just look at what makes us alive, then Earth (or any other planet) is as living as we are: it grows, changes shape, breathes, changes temperature and moves.
The only difference is it doesn't think, but then the majority of life on Earth doesn't either (that we know of, again, what is 'thinking'). Hell, Earth might even react in the same way a plant reacts to light and resource.
There's a song with pretty terrible lyrics and a cringe-worthy metaphor but the logic is sound, and it goes something like this: If a butterfly, which only lives for a day, landed on a tree and you asked it if the tree was alive, it would say "No, I've been here my whole life and it hasn't done a thing". The same goes for humans/Earth.