It seems the reason why nirvana never gets defined by people who see it is that when asked about it, they start to re-experience it, which they can do many times in a lifetime. And the experience of it is so intense -- utterly peaceful and still, beyond blissful, beyond words and mental chatter -- that they neither conceptualize it nor think to. Anyone who has experienced it is enlightened to some degree by the experience. Nirvana is experienced with the entire body (kalapas) and mind (cittas). Find someone, ask, pry, and see that this is the case. Conceptual definitions mislead.
"Meditators, there is an unborn, unmade, unbecome (un-brought-to-being), unconditioned (uncompounded). Meditators, if there were no unborn, unmade, unbecome, unconditioned, there would be no escape from what is born, made, become (brought-into-being), conditioned. But since there is, therefore an escape exists.'