A good base for a definition of life(From a user on the IRC)
1. The entity has a metabolism
2. The entity reacts with its surroundings.
3. The entity has some way to reproduce.
And a star has all three of these attributes.
Metabolism: Nuclear Fusion, This is a suns energy, without this, the star will die out.
Reactions: It has radioactive properties that help to protect its self.
Reproduction: At the end of a stars life, it may go super-nova, possibly creating a nebula, possibly creating more stars.
And some may use the counter, "Not all stars go supernova."
A reply to that is, not all humans can reproduce either.