impalpable

Incapable of being touched or felt; incorporeal, intangible.

But here thou canst not handle aught, neither make the folk ware of thee, not though thou shout thy throat hoarse. For thou and I walk here impalpable and invisible, as it were two dreams walking.

Not able to be perceived, or able to be perceived only with difficulty; insubstantial, thin.

On the benches lay figures covered with yellow linen, on which a fine and impalpable dust had gathered in the course of ages, but nothing like to the extent that one would have anticipated, for in these deep-hewn caves there is no material to turn to dust.

Not easily grasped (mentally) or understood.

What is happiness, anyhow? Is this one of its hours, or the like of it?—so impalpable—a mere breath, an evanescent tinge?

And I heard—him—it—this voice—other voices—all of them were so little more than voices—and the memory of that time itself lingers around me, impalpable, like a dying vibration of one immense jabber, silly, atrocious, sordid, savage, or simply mean, without any kind of sense.