10 letters · 18 points in Scrabble
adjective incapable of being perceived by the senses especially the sense of touch; - James Jeans
adjective imperceptible to the senses or the mind
adjective not perceptible to the touch
originFrom Middle French impalpable, from Medieval Latin impalpabilis. See im- + palpable.
Etymology from Wiktionary, CC BY-SA 3.0