Wow, no one pulled out the biological one, which, I think, is the most important.
Life - definition from Biology-Online.org
of being which begins with generation
, or germination
, and ends
with death; also, the time
during which this state
continues; that state
of an animal
in which all or any of its organs
are capable of performing all or any of their functions; used of all animal
and vegetable organisms
Although I think, perhaps, you are also asking what the purpose
of life is. If you were asking specifically for your own existance, then that's something you have to discover and decide on your own. To assume someone elses purpose is incredibly arrogant.
The purpose of life in general as we see it in its many forms on Earth? Eh, who knows, perhaps it's to be productive and constructive, perhaps it's to come out on top, perhaps it's to learn and evolve in such a way that benefits all others, there are all sorts of theories and reasons. In the end I think it might just be to entertain who/whatever put the universe here in the first place. You could go on and on and on...