What is enlightenment?
Well first it is a word symbol which is trying to describe a state of being. My definition of enlightenment would be an altered state of consciousness, meaning your level of awareness has become altered, and since we can never become less than we are now, it must mean an increase in our level of awareness.
Awareness of what? Of those things which you were previously unaware, which could be anything. It does not have to mean strictly spiritual enlightenment, however in the largest sense, all enlightenment is spiritual, because spirit is the next level of reality beyond this one, and is the only real place we can go. It is our home.