impalpable

adjective3

1. •
   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. — 1922
2. •
   Not able to be perceived, or able to be perceived only with difficulty; insubstantial, thin.
3. •
   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? — 1876