Lucidity is a personal experience, why do you need to define it?

It is a strange phenomenon for that first time.

If you see a rose dripping dew under a sunrise, and it is the first time you have ever seen anything, what can be said?
Another thing, is that there is no division between what is and what isn't, there is no question nor inhibition.

It is your division that is your non-lucidity, and your interjection that is against. Defining should be done with great caution, it can create much questioning and doubt, and does not take for granted that which is, which is (if you have have experience with dreams you will know) the catalyst (in a backwards way) for everything, including lucidity.

If you let lucidity, it is there. If you keep asking those who can never answer you truthfully, then you are just creating another problem. Another person's truth can never be your own, truth is subjective - for you to know what lucidity is, you must be lucid. When you are lucid, you will understand, but otherwise the asking of the question is going to be a barrier.