The question is not so much, what is enlightenment? The question is, what are we doing every day to purify and open to our full inner potential? If we do that, we will begin to get a flavor of what enlightenment is soon enough. Then it is not a theory or a philosophical determination anymore. It is by direct experience, and we can very simply put it in our own words.
The great 19th century yogi, Lahiri Mahasaya put it in his own words this way: "Enlightenment is a merging of emptiness with euphoria."
Many who have been doing deep meditation and spinal breathing pranayama for a while will know that this simple statement is true.
This forum is for sharing experiences on the road to enlightenment. Seeing milestones as we travel along can encourage us to keep up our practices. On the other hand, we may see very few milestones, and one day suddenly find ourselves at the destination. It all depends on how our purification is happening inside. Each person is unique in that. We all go at our own speed and in our own way. There is no set pattern for how it will happen. But if we keep up our practices day in and day out for as long as it takes, it will happen!