With that said, a more complicated definition might be better. Science tells us that the brain remembers everything but no one literally remembers everything. People think that they are their consciousness, but there is something that "sits behind us" which chooses what we remember and what we forget. When you encounter people who always seem to forget certain things entirely, the thing behind them may be at work. When someone comes to appreciate that what they think is themselves is really a mask, or a carving, or a puppet created by the one who sits behind them, they may be able to enter into a dialogue with that being and in doing so they may become enlightened. That being in turn has been described in various philosophies as God or a creation of God, as the soul or other things, but any philosophy worth its salt (even modern psychology) agrees that it exists.
I had a dream once where God sent tentacles into the earth (kind of a gross image, I know) and each of us is one of those tentacles. When the tentacle or tendril enters the earth, it gets clothed in a material body and begins to forget itself. The older we get, the more most of us forget but if we can remember then maybe that is enlightenment.