According to Osho, the unspeakable and ungraspable is your buddha-nature - at once obvious to the knower and mysterious to the mind. It is your original, untouched core, reachable only by you, revealed through innocence and witnessing. Dropping masks, you discover a silent, empty, oceanic consciousness: the 'original face' beyond words and concepts. Knowing it, you feel at home in the cosmos and need be no one else.
It’s your deepest, simple, silent self that you meet by just watching inside, not by thinking or talking.